Your FREE Kaplan Nursing Entrance Exam (KNAT) Practice Test 2026 – 240+ Q&A

Correct answer: Octopuses are surprisingly intelligent invertebrates

The passage calls the octopus one of the most intelligent invertebrates and lists skills once credited only to animals with backbones, so its main idea is that octopuses are surprisingly intelligent invertebrates. The claim that octopuses are about as bright as other invertebrates contradicts 'among the most intelligent.' That octopuses can recognize each of their human handlers is one supporting example, not the main idea, and the claim that octopuses are deeply attached to their human keepers reads an emotional bond into a passage that mentions only recognition.

Correct answer: Ancient rock paintings showing lakes and grazing herds

The passage says rock paintings show that the region once held lakes, grasslands, and herds of grazing animals, so the evidence is ancient rock paintings showing lakes and grazing herds. Ancient rock layers showing dried lakes and sand dunes swap the paintings for geology the passage never mentions. Records of a shifting climate over thousands of years and climate studies of the grasslands that once grew there are also not cited; the passage names the climate change as the cause of the drying, not as the evidence of the green past.

Correct answer: The technician acted promptly and took the initiative

Moving the samples to the backup cooler and starting the emergency generator immediately, 'before anyone had to ask,' shows that the technician acted promptly and took the initiative. The idea that the technician had been told to protect the samples contradicts 'before anyone had to ask.' The idea that the technician acted rashly and ignored the lab rules is unsupported, since both actions were sensible emergency steps, and the idea that the technician cared more for the samples than safety is unsupported, since nothing in the passage puts anyone at risk.

Correct answer: Distrust and disbelief

The residents 'doubted that the project would ease the traffic problems,' so skepticism here means distrust and disbelief toward the mayor's promise. Disinterest and apathy would mean the residents did not care, yet they held a clear opinion about the plan. Curiosity and interest suggest open-minded wondering rather than doubt, and resentment and anger describe hostility that the sentence never mentions.

Correct answer: To explain how the sound of thunder is produced

The passage traces a chain of cause and effect: the bolt heats the air so suddenly that it expands explosively, 'producing the sound we call thunder.' Its purpose is therefore to explain how the sound of thunder is produced. To show that lightning is hotter than the surface of the sun covers only the opening comparison, which leads into the main point. To describe the strange colors of the storm sky brings in a detail the passage never mentions, and to warn readers about the dangers of lightning is not the aim, since the passage gives no safety advice.

Correct answer: Opponents doubted the lights would stay bright in cloudy winters

The passage states that opponents 'questioned whether the lights would stay bright through the long, cloudy winters,' so opponents doubted the lights would stay bright in cloudy winters. The claim that supporters noted the solar lights would raise electricity bills reverses the supporters' point that the lights would lower bills. The claim that the council postponed its vote on the solar lights until spring contradicts the statement that the council voted to install them, and the claim that the council soon voted to take down the lights after one cloudy winter turns the opponents' worry into an event the passage never describes.

Correct answer: She felt nervous even after months of preparation

Her hands shook and she nearly forgot the opening notes as she walked onstage, so she felt nervous even after months of preparation. The claim that she felt calm and confident in front of the audience contradicts her shaking hands. The idea that she had not practiced the piece for long enough ignores the months of practice the passage mentions, and the idea that she was more afraid of the audience than of the music is never stated; the passage gives no cause for her nerves.

Correct answer: Close inspection

Her peers 'carefully examined her data and repeated her experiments,' so scrutiny here means close inspection. Open criticism is a near miss, but the peers checked the work rather than attacking it. Public attention is another sense of the word that does not fit peers repeating experiments, and cautious approval skips the checking; the peers accepted the results only after their review.

Correct answer: Wind turbines convert moving air into electricity

Both sentences describe how the push of the wind spins the blades, shaft, and generator to produce current, so the central idea is that wind turbines convert moving air into electricity. The claim that wind turbines use electricity from the existing grid reverses the direction of the flow; the turbines supply current rather than consume it. The claim that wind turbines save electricity for homes and offices describes storage, which the passage does not mention, and the claim that wind turbines supply electricity for the lowest cost makes a price comparison the passage never makes.

Correct answer: To create a lonely mood of quiet and stillness

Swings drifting with no riders, a forgotten ball, and silence where laughter once rang out all describe emptiness, so the author's aim is to create a lonely mood of quiet and stillness. To recall the happy laughter of children at play is too narrow; the laughter is mentioned only as something now missing. To warn that the town neglected its playground reads blame into the scene that the passage never states, and to build a sense of fear and danger at nightfall misjudges the tone, which is quiet and sad rather than threatening.

Correct answer: Keeping records of the weather

The passage lists the keepers' duties as keeping the lamp burning, recording the weather, and rescuing sailors, so keeping records of the weather was one of them. Warning the distant towns of bad weather is a near miss; the keepers recorded the weather, but the passage never says they sent warnings. Repairing the ships that had run aground misreads the rescue duty, since the keepers saved the sailors, not the vessels, and guiding ships into the harbor safely is not mentioned among their tasks.

Correct answer: The marketing claims may be inaccurate

The store advertised locally grown produce, yet the apple stickers named a country thousands of miles away, so the marketing claims may be inaccurate. The idea that the local farms may be exporting fruit reverses the direction of the trade; the stickers show the apples came from far away. The ideas that the local buyers may like foreign food and that the imported apples may be far cheaper bring in shopper tastes and prices, which the passage never discusses.

Correct answer: Friendly and cordial

The nations shook hands and pledged to cooperate, so an amicable agreement is friendly and cordial. Formal and official describes the setting of a treaty, not the goodwill the handshake shows. Lasting and permanent confuses the word with the plans for 'the years ahead,' and reluctant and grudging contradicts the warm handshake that ended the talks.

Correct answer: The printing press made books faster and cheaper to print

The passage contrasts slow, costly hand copying with the quick, cheap production that printing allowed. Its main point is that the printing press made books faster and cheaper to print. "The printing press reached Europe in the fifteenth century" is a supporting detail, not the main point. "The printing press put most hand copyists out of a job" is a claim the passage never makes. "The printing press kept reading material rare and costly" reverses the passage, which says hand copying did that.

Correct answer: Short and direct

The supervisor answered 'each question with a single word,' so terse replies are short and direct. Vague and evasive is a near miss, but one-word answers can be perfectly clear; the passage describes their length, not any dodging. Shy and hesitant reads an emotion into the replies that the passage never mentions, and calm and polite describes manner rather than the brevity the sentence stresses.

Correct answer: Bamboo grows fast and quickly regrows once harvested

The passage says bamboo is one of the fastest-growing plants and 'regrows so quickly after harvest' that it counts as renewable, which directly supports that bamboo grows fast and quickly regrows once harvested. The claim that bamboo is slow to regrow and must be replanted often contradicts that quick regrowth. The claim that most bamboo plants gain nearly a full meter in a day stretches 'some species' to most of them, and the claim that bamboo is the fastest grower among the world's plants overstates 'one of the fastest-growing.'

Correct answer: They feared the rising water would flood the house

The family hurried to carry photo albums and papers to the attic while glancing nervously out the windows as the water rose past the porch steps, so they feared the rising water would flood the house. The idea that they expected a rescue boat to arrive within hours is unsupported, because no rescue is mentioned. The idea that they valued their keepsakes above their own safety reads too much into what they chose to carry. The idea that they had survived many floods like this one before is not supported and does not fit their nervous hurry.

Correct answer: To explain what causes coral bleaching and its effects

The passage gives the cause of bleaching, water that is too warm, and its effects, pale coral that is far more likely to die, so its purpose is to explain what causes coral bleaching and its effects. To describe the life cycle of the tiny algae in corals goes beyond the passage, which mentions the algae only as the source of the coral's color. To argue that people should act to protect coral reefs gives the passage a persuasive aim, but it calls for no action. To contrast coral in warm seas with coral in cool seas invents a comparison, since cool-water coral is never discussed.

Correct answer: Nurses came to value it after the early complaints

Nurses at first complained that the system slowed them down, but within a few weeks most agreed it saved time and reduced errors, so nurses came to value it after the early complaints. The claim that nurses praised it as a time saver from the first day ignores those early complaints. The claim that nurses found it saved time but led to more errors contradicts the statement that it reduced errors, and the claim that nurses dropped the system after a few weeks of trials reverses what happened after those weeks.

Correct answer: Twelve seconds

The passage states that the aircraft 'stayed aloft for only twelve seconds,' so the first powered flight lasted twelve seconds. Twelve hours keeps the right number with the wrong unit. Nineteen seconds and nineteen hours take the number from the year 1903 rather than from the length of the flight.

Correct answer: Productive

Publishing two or three books a year for nearly three decades describes a large output, so "prolific" here means productive. Celebrated echoes "was known for," but the word describes how much she wrote, not her fame. Profitable sounds similar to "prolific," but the sentence says nothing about earnings. Persistent captures how long she kept writing, not how much she produced.

Correct answer: Understanding the brain's role took centuries of study

The passage moves from an old belief about the heart to the scientists who, 'only through centuries of careful study,' came to understand the brain's role, so its main idea is that understanding the brain's role took centuries of study. That people once saw the heart as the center of thought is the starting detail, not the main idea. The claim that scientists found it was the heart that governs emotion turns the old belief into a finding, and the claim that careful study led scientists to doubt the brain's role reverses the passage, in which study revealed the brain's true role.

Correct answer: Because the cliff edge is hidden and the rock is unstable

The guide explains that just beyond the ropes the cliff edge is hidden by thick brush and the rock could crumble without warning, so she warns the group because the cliff edge is hidden and the rock is unstable. The reason 'because the brush beyond the ropes is full of rare plants' and the reason 'because the thick brush is home to snakes and wild animals' both misread the brush, which matters only because it hides the cliff edge. The reason 'because the marked path is the fastest way to the cliff' is never mentioned; the guide talks about danger, not speed.

Correct answer: Compact and clear

The proposal 'conveyed every necessary point in just two pages without a single wasted word,' so concise here means compact and clear. Quick and rushed is a near miss, but a rushed proposal would not cover every necessary point. Formal and polished and bold and persuasive describe style and force, while the committee praised the proposal for its economy of words.

Correct answer: Antarctica holds about seventy percent of Earth's fresh water

The first sentence states that Antarctica holds about seventy percent of Earth's fresh water, locked in its ice sheet. The claim that the continent's extreme cold is what makes Antarctica a desert gives the wrong reason; the passage says it is a desert because almost no precipitation falls. The claim that Antarctica's massive ice sheet is shrinking faster each decade is never mentioned; the passage describes the ice sheet but says nothing about how it changes. The claim that Antarctica is the largest desert on Earth by total land area is never stated; the passage calls it a desert but does not rank deserts by size.

Correct answer: The customer put off the final choice for now

The customer studied the contract, asked pointed questions, and set down the pen without signing, so the customer put off the final choice for now. The idea that the customer turned down the offer for good goes too far; not signing yet is not a final refusal. The idea that the customer did not understand the salesman clashes with the pointed questions, which suggest close understanding, and the idea that the customer was certain the salesman was lying reads a suspicion into the scene that the passage never states.

Correct answer: To explain how sleep makes memories stronger

The passage says that during rest the brain replays and strengthens the day's connections, helping us hold on to what we learned, so its purpose is to explain how sleep makes memories stronger. To explain how the brain forms new connections misreads the process; the connections form during the day and are strengthened in sleep. To explain why students should get more sleep assigns a persuasive goal the passage does not have, and to explain how the brain creates our dreams mistakes 'replays' for dreaming, which the passage never mentions.

Correct answer: It left fertile silt on the farmland each year

The passage says the yearly flood 'spread rich silt across the fields' and that this natural fertilizer let farmers grow abundant crops, so it left fertile silt on the farmland each year. 'It washed soil away from the fields to the sea' reverses what the flood did, because it brought rich soil onto the fields. 'It moved water out to farms far from the river' names an irrigation benefit the passage never mentions. 'It drowned the insects that were eating plants' names a pest-control benefit that is also absent from the passage.

Correct answer: Dull and wearisome

The reviewer complained that the three-hour film 'dragged through scene after scene in which almost nothing happened,' so tedious here means dull and wearisome. Slow and unhurried is a near miss, but 'unhurried' sounds neutral or even pleasant, and the reviewer was complaining. Somber and serious describes a dark mood the review never mentions, and confused and vague describes a lack of clarity, not the boredom of scenes where nothing happens.

Correct answer: The writers hold opposite beliefs about one town

The first writer calls the town a peaceful escape, while the second calls it dull and isolated, so the writers hold opposite beliefs about one town. The idea that the writers describe two different mountain towns contradicts the opening line, which says both describe the same town. The claim that both writers feel the same way about the town ignores their contrast, and the claim that both writers see the town as dull and isolated fits only the second writer.

Correct answer: Temporarily quiet

The volcano had been dormant for centuries and then 'suddenly rumbled to life,' so dormant here means temporarily quiet. Permanently extinct is the villagers' mistaken belief, and the eruption proves the volcano was not dead. Recently formed contradicts the centuries of quiet, and mildly active does not fit a mountain so still that people assumed it would never wake.

Correct answer: Honey stays fully edible for thousands of years

The passage opens by saying honey never spoils, then supports that with tomb honey that is still edible. Its main idea is that honey stays fully edible for thousands of years. "Honey was placed in tombs to feed dead pharaohs" gives a purpose the passage never states. "Honey resists spoiling due to its high moisture" reverses the cause, because the passage credits low moisture and natural acidity. "Honey is the oldest food found in ancient tombs" claims a record the passage does not make.

Correct answer: He struggled to express his thoughts clearly

The patient paused often, repeated himself, and struggled to find the right words, so he struggled to express his thoughts clearly. The idea that he was unsure which symptoms he really had mistakes a struggle for words for doubt about the symptoms themselves. The idea that he wanted to keep some of his symptoms hidden reads a motive into the scene that the passage never gives, and the idea that he was too worn out to finish his full account is not supported; nothing says he stopped before describing his symptoms.

Correct answer: Thorough

The regulations covered 'everything from equipment inspections and emergency drills to the proper storage of every chemical,' so comprehensive here means thorough. Mandatory describes whether rules must be followed, not how much they cover. Lengthy and intricate are near misses about size and difficulty, but the sentence stresses the range of topics covered, not the length of the rules or how hard they are to follow.

Correct answer: To find work and escape discrimination

The passage says people moved 'in search of jobs and an escape from harsh discrimination,' so they went to find work and escape discrimination. To escape harsh droughts and dust storms attaches 'harsh' to the weather rather than to discrimination. To leave crowded cities for peaceful farmland reverses the direction of the move, which went from the rural South to cities, and to buy cheap farmland on the western frontier is not mentioned; the migrants headed for cities in the North and West.

Correct answer: To build curiosity before the main lesson starts

The professor posed a puzzling riddle, let students whisper guesses, and only then revealed that its answer would unlock the day's topic, so the aim was to build curiosity before the main lesson starts. To test what students already knew about the topic mistakes the guessing for a quiz, though no answers were checked. To give the class a short break before the lecture ignores that the riddle opened the lecture and led straight into it, and to reward the students who guessed the answer is unsupported; no one is said to have guessed it.

Correct answer: Keystone species play vital roles in keeping an ecosystem balanced

The passage says a keystone species holds an entire ecosystem together and that removing it can unravel the web of life, so the main idea is that keystone species play vital roles in keeping an ecosystem balanced. "Keystone species are large animals living in an ecosystem" adds a size claim the passage never makes. "An ecosystem stays in balance as long as most of its species remain" is contradicted: losing the keystone alone can unravel the whole web. "The balance of an ecosystem decides which species will be its keystone" reverses the cause, since the passage says the keystone provides the balance.

Correct answer: She was dedicated and eager to contribute

Arriving an hour early, organizing the supply room without being asked, and staying late to finish the labeling all point to one inference: she was dedicated and eager to contribute. "She was nervous and worried about her job" does not fit someone who acted on her own initiative, and no sign of worry is given. "She was ambitious and seeking a promotion" guesses at a motive the passage never mentions. "She was overworked and behind on her work" misreads the extra effort, because she took on extra tasks by choice rather than catching up on assigned ones.

Correct answer: Unclear and imprecise

In context, "vague" most nearly means unclear and imprecise: the promises never explained how any goal would actually be achieved, so they lacked specifics. "Lofty and noble" describes how the promises sounded, not their lack of detail. "Repeated and familiar" is not suggested anywhere in the passage. "Hopeful and optimistic" matches their appeal, but the word the passage chose criticizes the missing detail.

Correct answer: Spiders have two main body parts and eight legs

The passage states that spiders have eight legs and two main body parts, so the answer is "Spiders have two main body parts and eight legs." "Insects have two main body parts and six legs" gives insects the spider body count; the passage says insects have three. "Spiders have three main body parts and six legs" gives spiders the insect counts. "Insects have three main body parts and eight legs" gives insects the spider leg count; the passage says insects have six.

Correct answer: He was relieved that the rain ended a long dry spell

The slow, grateful breath he lets out as the rain soaks the cracked earth after the drought finally broke shows that he was relieved that the rain ended a long dry spell. "He was worried that the rain would flood his field" ignores the word grateful. "He was weary after a long day of hard work in the field" mistakes a grateful sigh for tiredness; the passage mentions no day of work. "He was doubtful that the rain would last for long" adds a worry the passage never suggests.

Correct answer: To explain that many medicines originate from plants

The passage opens with its point, "Many medicines come from plants," and uses willow bark only as an example, so its purpose is to explain that many medicines originate from plants. "To explain how willow bark was used to ease fever" mistakes the supporting example for the purpose. "To explain why aspirin from willow bark relieves fever" is wrong because the passage notes that people used the bark before chemistry could explain why it worked. "To explain why modern medicines work better than plants" makes a comparison the passage never draws.

Correct answer: Thoughtful and sensitive in speech

In context, "tactful" most nearly means thoughtful and sensitive in speech: the negotiator chose her words with care so that no one left feeling insulted. "Calm and composed in a heated debate" describes keeping one's temper, not sparing others' feelings. "Firm and persuasive in negotiation" fits her job but not the word, which is about avoiding offense. "Quiet and reserved in their manner" is wrong because she was choosing her words, not holding back from speaking.

Correct answer: Recycling cans saves energy, yet many are still thrown away

The passage pairs the energy saved by recycling with the cans that still go to landfills, so the main idea is that recycling cans saves energy, yet many are still thrown away. "Televisions use a lot of power, but few people unplug them" turns a comparison used for scale into the topic, and the passage says nothing about unplugging. "Aluminum breaks down fast, so landfills hold few empty cans" contradicts the statement that the metal can take centuries to break down. "Metal lasts centuries, so landfills are safe spots for cans" presents as safe the outcome that the passage treats as a problem.

Correct answer: The alibi the suspect gave may be false

The suspect claims he was home all evening, but a parking receipt puts his car downtown at the hour of the crime. The passage therefore most strongly suggests that the alibi the suspect gave may be false. "The suspect may really have stayed home" ignores the receipt, which is the evidence against his claim. "The detective may have proven his guilt" goes too far, because a car downtown does not show who committed the crime. "The receipt may belong to someone else" has no support, since the passage says the receipt placed his car downtown.

Correct answer: Recently founded

In context, "fledgling" most nearly means recently founded. The phrase "in its first year" marks the company as new. "Highly ambitious" describes plans or attitude, not how old the company is. "Quickly growing" restates a separate detail, "grew rapidly"; it is not the meaning of "fledgling." "Barely surviving" contradicts the passage, which describes the company doubling its staff and opening new offices.

Correct answer: Warring city-states agreed to a truce during the games

The passage states this detail in so many words: during the games, warring city-states agreed to a truce, so the answer is "warring city-states agreed to a truce during the games." "Warring city-states held the games to honor their athletes" misreads the festivals, which honored the gods. "Warring city-states sent guards with athletes during the games" is not stated; a truce, not an armed escort, let athletes travel safely. "Warring city-states kept fighting while the games went on" contradicts the truce the passage describes.

Correct answer: To hook readers with a warm scene before raising serious issues

The article moves from a pleasant sensory detail to the struggles of family-run shops, so the author most likely wants to hook readers with a warm scene before raising serious issues. "To show that family-run shops are still thriving despite hard times" contradicts the discussion of shops struggling to survive. "To suggest that family-run shops should sell more fresh bread" offers advice the article never gives. "To describe a bakery with care before reviewing its bread and prices" treats the article as a review, but it turns to struggling shops, not prices.

Correct answer: Limited in amount

In context, "scarce" most nearly means limited in amount: the project's success was in doubt because there was not enough funding. "Delayed in arrival" confuses scarcity with the approaching deadline. "Restricted in use" describes money set aside for one purpose, not too little of it. "Uncertain in origin" borrows the word uncertain, which the passage applies to the project's success, not to where the money came from.

Correct answer: Creatures flourish near deep-sea vents using chemical energy

The passage describes whole communities living around the vents in total darkness and drawing energy from chemicals rather than sunlight, so the central idea is that creatures flourish near deep-sea vents using chemical energy. "Creatures living near deep-sea vents need sunlight and chemicals" contradicts the total darkness. "Water near the deep-sea vents is too hot for life" contradicts the thriving communities. "Water near the deep-sea vents is heated by its minerals" misreads a detail: the water is mineral-rich, but the Earth's interior heats it.

Correct answer: To lift and fortify

In context, "bolster" most nearly means to lift and fortify: the pep talk reminded the team how far they had come in order to raise their spirits. "To calm and settle" would quiet the team rather than build up its confidence. "To praise and reward" describes recognizing past work, while the talk aimed to strengthen spirits before the game. "To test and challenge" would put the players under pressure, the opposite of the encouraging purpose.

Correct answer: Transparent skin lets the glass frog escape the notice of predators

The main idea is that 'transparent skin lets the glass frog escape the notice of predators': the passage describes the see-through skin and then explains that it lets the frog blend into leaves and hides its outline from predators below. 'Transparent skin lets light reveal the heart of the glass frog' is only a supporting detail from the first sentence, not the point the passage builds to. 'Transparent skin lets predators spot the glass frog much more easily' reverses the passage, which says the skin conceals the frog. 'Transparent skin lets light warm the body of the glass frog' is never mentioned; the passage gives camouflage, not warmth, as the benefit.

Correct answer: The shopkeeper was hoping to close up and leave before the storm

The most reasonable inference is that 'the shopkeeper was hoping to close up and leave before the storm': locking the till an hour early, tidying, and glancing between the clock and the storm clouds all point to finishing up and leaving before the weather arrives. 'The shopkeeper was expecting a big late rush of customers before the storm' conflicts with locking the till early, which a shopkeeper would not do while expecting sales. 'The shopkeeper was growing bored and fed up because the shop was slow' explains the clock-watching but ignores the early locking and the attention to the storm clouds. 'The shopkeeper was getting the shop ready to welcome the owner' has no support in the passage, which mentions no visitor.

Correct answer: Fair and impartial

In context, "unbiased" means 'fair and impartial': the report weighed every proposal with equal care and refused to favor any group. 'Thorough and detailed' describes the care the report took, but being thorough is different from being free of bias; a thorough report can still take sides. 'Cautious and noncommittal' misreads the refusal to favor a group as an unwillingness to reach any judgment, which the passage does not say. 'Tactful and polite' describes manners and tone, not the even-handed treatment of the proposals.

Correct answer: Because later waves can do more damage than the initial surge

The passage says officials warn people to stay away for hours 'because later waves can do more damage than the initial surge': a tsunami is a series of waves, and the first is often not the largest. 'Because the waves can take several hours to reach the coast' is not the reason the passage gives; it explains the warning by the danger of later waves in the series, not by how long the waves take to arrive. 'Because the coast can remain flooded for hours after the first wave' is never stated; the passage is concerned with further waves, not standing water. 'Because a single towering wave can do more damage than a series' contradicts the passage's opening point that a tsunami is not a single towering wave but a series of waves.

Correct answer: To convince the council to expand its child care subsidies

The author's main purpose is 'to convince the council to expand its child care subsidies': the op-ed lists rising family costs and then calls on the council to act before more parents leave the workforce. 'To praise the council for its past support of child care subsidies' misses the call for action; the author wants more support, not thanks for the current level. 'To blame the council for past cuts to child care subsidies' invents cuts the passage never mentions. 'To show the council how other towns expand child care subsidies' treats the op-ed as a comparison with other places, but it mentions no other towns; it argues that this council should act.

Correct answer: Easily passed to others

In context, "contagious" means 'easily passed to others': the recruit's enthusiasm passed from person to person until even the most jaded crew members shared it. 'Likely to make others ill' is the medical sense of the word, but here it describes enthusiasm, which made the crew work harder rather than sicken them. 'Openly shown to others' describes enthusiasm that is visible, but the passage stresses that it spread, not merely that it was displayed. 'Hard for others to ignore' describes something noticeable, yet noticing an attitude is not the same as taking it on, which is what the crew did.

Correct answer: Fold in the eggs

The recipe says to 'fold in the eggs' last, after the earlier steps and just before baking. 'Preheat the oven' is listed as the first step, not the last. 'Mix in the dry ingredients' misreads the order: the card says to mix the dry ingredients first, not last. 'Put it in the oven to bake' is the baking itself, so it cannot be the step that comes before baking.

Correct answer: The scientists differ on how secure the recovery of the species is

'The scientists differ on how secure the recovery of the species is': one reads the rising counts as real recovery, while the other warns that the gains are fragile and one bad season could erase them. 'The scientists agree that the recovery of the species is now secure' ignores the second scientist, who calls the gains fragile. 'The scientists disagree on whether the counts in the reserves are accurate' misplaces the dispute; the second scientist accepts the gains and questions only how lasting they are. 'The scientists agree on how much larger the reserves will need to be' is not stated; neither scientist makes any recommendation about reserves.

Correct answer: To capture the disorienting emptiness of the vast landscape

The author describes the salt flats this way 'to capture the disorienting emptiness of the vast landscape': endless blinding white, a flat and featureless surface, and a lost sense of distance all build a feeling of overwhelming space. 'To warn travelers about the blinding glare of the white salt' turns one image, "blinding white," into a safety warning the passage never gives. 'To explain why distant mountains look smaller than they are' misreads the passage, which says a far-off mountain seems close, not that it looks small. 'To describe how travelers measure distance across the flats' contradicts the passage, which says travelers lose all sense of distance.

Correct answer: 16

Multiplication comes before addition and subtraction, so 3 × 4 = 12 first; then 6 + 12 = 18 and 18 - 2 = 16. Working left to right without that priority gives (6 + 3) × 4 - 2 = 34. Subtracting before multiplying gives 6 + 3 × 2 = 12. Doing both the addition and the subtraction first gives (6 + 3) × (4 - 2) = 18.

Correct answer: 14

Work inside the parentheses first: 5 - 3 = 2. Then apply the exponent (2 squared = 4), multiply (4 × 3 = 12), and add last: 2 + 12 = 14. Adding before multiplying gives (2 + 4) × 3 = 18. Multiplying before squaring gives 2 + (2 × 3) squared = 2 + 36 = 38. Squaring each number inside the parentheses gives 25 - 9 = 16, and 2 + 16 × 3 = 50.

Correct answer: 14

Division and multiplication come before addition: 24 ÷ 6 = 4 and 2 × 5 = 10, so the value is 4 + 10 = 14. Adding 6 + 2 before dividing gives 24 ÷ 8 × 5 = 15. Working strictly left to right gives 4 + 2 = 6 and then 6 × 5 = 30. Multiplying the two results (4 × 10) instead of adding them gives 40.

Correct answer: 32

The parentheses give 2 + 1 = 3; division and multiplication then go left to right (12 ÷ 3 = 4, and 4 × 2 = 8), and the subtraction comes last: 40 - 8 = 32. Ignoring the parentheses gives 40 - 12 ÷ 2 + 1 × 2 = 40 - 6 + 2 = 36. Multiplying before dividing gives 12 ÷ (3 × 2) = 2, and 40 - 2 = 38. Subtracting before multiplying gives (40 - 4) × 2 = 72.

Correct answer: 19

The parentheses give 4 + 6 = 10 and the exponent gives 3 squared = 9; then 100 ÷ 10 = 10, and 10 + 9 = 19. Treating 3 squared as 3 × 2 = 6 gives 10 + 6 = 16. Ignoring the parentheses gives 100 ÷ 4 + 6 + 9 = 40. Making both mistakes gives 25 + 6 + 6 = 37.

Correct answer: 0.75

Divide the numerator by the denominator: 3 ÷ 4 = 0.75. Dividing the denominator by the numerator, 4 ÷ 3, gives about 1.33. Writing the two digits of 3/4 after a decimal point gives 0.34, which is not how a fraction converts. Doing the same with the fraction flipped to 4/3 gives 0.43, which makes both mistakes.

Correct answer: 3/5

Six tenths is 6/10, and dividing the numerator and denominator by 2 gives 3/5 in lowest terms. The fraction 6/10 has the right value but is not reduced, so it is not in lowest terms. The fraction 2/3 is about 0.67, a common mix-up with 0.6. The fraction 5/3 flips the answer and is greater than 1.

Correct answer: 0.45

A percent means per hundred, so divide by 100 by moving the decimal point two places to the left: 45% = 0.45. 4.5 moves the point only one place, which divides by 10. 0.045 moves it three places, which divides by 1,000. 45.0 drops the percent sign without dividing at all.

Correct answer: 12.5%

Divide 1 by 8 to get 0.125, then multiply by 100 to get 12.5%. Writing the decimal 0.125 with a percent sign, without multiplying by 100, gives 0.125%. Reading 1/8 as the decimal 0.18 and multiplying by 100 gives 18%, which is not the value of 1/8. Reading 1/8 as 0.18 and also skipping the multiplication by 100 makes both mistakes and gives 0.18%.

Correct answer: 1/8

The digits 125 are thousandths, so 0.125 = 125/1000, and dividing both numbers by 125 gives 1/8. The fraction 125/1000 has the right value but is not reduced. The fraction 5/40 is only partly reduced (both numbers divided by 25) and still shares a factor of 5. The fraction 3/25 equals 0.12, which comes from cutting off the last digit of 0.125.

Correct answer: 0.7, 72%, 3/4

Write all three as decimals: 0.7, 72% = 0.72, and 3/4 = 0.75, so the order from least to greatest is 0.7, 72%, 3/4. The list 3/4, 72%, 0.7 gives the same values from greatest to least. The list 3/4, 0.7, 72% treats 3/4 as 0.34. The list 72%, 3/4, 0.7 treats 72% as 0.072 and 3/4 as 0.34.

Correct answer: 25

The ratio is 2 parts concentrate to 5 parts water. Going from 2 to 10 parts of concentrate multiplies by 5, so the water is 5 × 5 = 25 parts. Applying the ratio upside down gives 10 × 2/5 = 4. Adding the difference of 3 instead of scaling gives 10 + 3 = 13. Adding the 10 parts of concentrate gives 35 parts, the whole mixture rather than the water alone.

Correct answer: 15

Cross-multiply: 4 × x = 3 × 20, so 4x = 60 and x = 15. Stopping at the scale factor (20 ÷ 4 = 5) gives 5. Adding 16 to the numerator because 16 was added to the denominator gives 3 + 16 = 19; proportions scale by multiplying, not adding. Forgetting to divide by 4 leaves 60.

Correct answer: 90

Each instructor has 18 students, so 5 instructors have 18 × 5 = 90 students. Adding 18 + 5 = 23 or subtracting 18 - 5 = 13 combines the numbers without using the ratio. Adding the 5 instructors to the 90 students gives 95, the total number of people rather than the number of students.

Correct answer: 4 cups

Flour is 3 times the sugar, so the sugar is 12 ÷ 3 = 4 cups. Subtracting the 3 in the ratio from 12 gives 9 cups; a ratio scales by multiplying or dividing, not by subtracting. Multiplying 12 by 3 instead of dividing gives 36 cups. Adding the flour and sugar together gives 16 cups, the total rather than the sugar alone.

Correct answer: $15

The price per pound is $6 ÷ 4 = $1.50, so 10 pounds cost 10 × $1.50 = $15. Pricing only the 6 extra pounds gives $9. Adding the 10 pounds to the $6 price, as if the numbers simply add, gives $16. Adding $6 for the 6 extra pounds, as if each pound cost $1, gives $12.

Correct answer: 175 miles

Each inch stands for 25 miles, so 7 inches stand for 7 × 25 = 175 miles. Adding 25 + 7 gives 32 miles. Multiplying 7 × 20 and dropping the 5 gives 140 miles. Multiplying the 20 by 7 but adding the 5 only once gives 140 + 5 = 145 miles.

Correct answer: 24

Thirty percent is 0.30, and 0.30 × 80 = 24 (10% of 80 is 8, and three times that is 24). Stopping at 10% gives 8. Subtracting 30 from 80 treats the percent as a plain number and gives 50. Finding the remaining 70% gives 56.

Correct answer: $30

A 25% markdown takes off 0.25 × $40 = $10, so the sale price is $40 - $10 = $30. Dividing $40 by 1.25 undoes a markup instead of applying a discount and gives $32. Writing 25% as 0.025 makes the discount $1 and the price $39. Adding the $10 instead of subtracting it gives $50.

Correct answer: 85%

Divide the part by the whole: 51 ÷ 60 = 0.85, and multiplying by 100 gives 85%. Multiplying 0.85 by 10 instead of 100 gives 8.5%. The 9 missed questions are 9 ÷ 60 = 0.15 = 15%, the share answered incorrectly. Using the 9 missed questions and also multiplying 0.15 by 10 instead of 100 makes both mistakes and gives 1.5%.

Correct answer: 75

If 20% of the number is 15, the number is 15 ÷ 0.20 = 75. Taking 20% of 15 instead gives 3, which uses the wrong base. Subtracting that 3 from 15 gives 12, and adding it gives 18; both still treat 15 as the whole instead of the part.

Correct answer: 15%

The percent increase is 15%. The change is 230 - 200 = 30 patients, and dividing that change by the original 200 gives 0.15, or 15%. 30% treats the 30-patient change itself as the percent; 115% is the new count as a percent of the old one (230 ÷ 200), not the increase; and 130% makes both slips, counting the 30 extra patients as 30% and adding that to 100%.

Correct answer: $9

The tip is $9: 18% written as a decimal is 0.18, and 0.18 × 50 = 9. Adding that tip back onto the bill gives $59, the bill plus the tip rather than the tip itself; $18 reads the 18% as 18 dollars; and $32 comes from subtracting 18 from 50 as if the 18% were $18.

Correct answer: 5

The value of x is 5. Subtracting 7 from both sides gives 3x = 15, and dividing both sides by 3 gives x = 5. Stopping at 15 skips the division; 12 subtracts 3 from 15 instead of dividing by 3; and 9.67 adds 7 to 22 instead of subtracting it, so 3x = 29 and x = 29/3, about 9.67.

Correct answer: 36

The value of x is 36: multiplying both sides by 4 undoes the division, so x = 9 × 4 = 36. Dividing 9 by 4 instead gives 2.25; dividing 4 by 9 gives about 0.44; and 13 adds 4 to 9 instead of multiplying.

Correct answer: 5

The value of y is 5. Subtracting 2y from both sides gives 3y - 8 = 7, adding 8 gives 3y = 15, and dividing by 3 gives y = 5. Dividing 15 by 5, the original coefficient, gives 3; multiplying 15 by 3 gives 45; and subtracting 3 from 15 gives 12.

Correct answer: 5

The value of x is 5. Dividing both sides by 2 gives x + 3 = 8, and subtracting 3 gives x = 5. Stopping at x + 3 = 8 gives 8; multiplying only x by 2, so 2x + 3 = 16, gives 6.5; and distributing to 2x + 6 = 16 but then multiplying 10 by 2 instead of dividing gives 20.

Correct answer: 5

The value of x is 5. Subtracting 12 from both sides gives -4x = -20, and dividing both sides by -4 gives x = 5. Dividing -20 by 4 instead of -4 gives -5; adding 12 to -8 instead of subtracting it gives -4x = 4, so -1; and 1 makes both slips, adding the 12 and then dividing 4 by 4 instead of -4.

Correct answer: 18

The value of n is 18. Subtracting 4 from both sides gives n/3 = 6, and multiplying both sides by 3 gives n = 18. Adding 4 to 10 instead of subtracting it gives n/3 = 14, so 42; multiplying only n/3 and the 10 by 3 (n + 4 = 30) gives 26; and multiplying 10 by 3 while ignoring the 4 gives 30.

Correct answer: 2500 mg

There are 2500 mg in 2.5 grams: 1 gram is 1000 milligrams, so 2.5 × 1000 = 2500. Multiplying by 100 instead of 1000 gives 250 mg; dividing by 1000 converts in the wrong direction and gives 0.0025 mg; and dividing by 100 makes both slips and gives 0.025 mg.

Correct answer: 4000 mL

Four liters equals 4000 mL: 1 liter holds 1000 milliliters, and 4 × 1000 = 4000. Multiplying by 100 instead of 1000 gives 400 mL; dividing by 1000 converts in the wrong direction and gives 0.004 mL; and dividing by 100 makes both slips and gives 0.04 mL.

Correct answer: 300 cm

Three meters equals 300 cm: 1 meter is 100 centimeters, and 3 × 100 = 300. Multiplying by 1000, the meter-to-millimeter factor, gives 3000 cm; dividing 3 by 100 converts in the wrong direction and gives 0.03 cm; and dividing 3 by 1000 makes both slips and gives 0.003 cm.

Correct answer: 0.5 g

Five hundred milligrams equals 0.5 g: 1,000 milligrams make 1 gram, so 500 ÷ 1,000 = 0.5. Dividing by 10,000 (one zero too many) gives 0.05 g; dividing by 1,000,000, as if converting micrograms, gives 0.0005 g; and dividing 1,000 by 500 gives 2 g.

Correct answer: 750 mL

The patient receives 750 mL: 1 liter is 1,000 milliliters, so 0.75 × 1,000 = 750. Using 100 as the factor gives 75 mL; dividing by 1,000 converts in the wrong direction and gives 0.00075 mL; and dividing by 100 makes both slips and gives 0.0075 mL.

Correct answer: 4.5 kg

There are 4.5 kg in 4,500 grams: 1,000 grams make 1 kilogram, so 4,500 ÷ 1,000 = 4.5. Dividing by 100 instead of 1,000 gives 45 kg; dividing 1,000 by 4,500 inverts the division and gives about 0.22 kg; and dividing 100 by 4,500 makes both slips and gives about 0.022 kg.

Correct answer: 0.25 L

Two hundred fifty milliliters equals 0.25 L: 1,000 milliliters make 1 liter, so 250 ÷ 1,000 = 0.25. Dividing by 100 gives 2.5 L; dividing 1,000 by 250 gives 4 L; and 250,000 L multiplies by 1,000, converting in the wrong direction.

Correct answer: 95 degrees F

Thirty-five degrees Celsius equals 95 degrees F: 9/5 × 35 = 63, and 63 + 32 = 95. Adding 32 without multiplying gives 67 degrees F; multiplying by 5/9 instead of 9/5 gives about 19.4 + 32 = 51.4 degrees F; and stopping before adding 32 gives 63 degrees F.

Correct answer: 212 degrees F

One hundred degrees Celsius equals 212 degrees F, the boiling point of water: 9/5 × 100 = 180, and 180 + 32 = 212. Stopping before adding 32 gives 180 degrees F; subtracting 32 from 100, the first step of the Celsius formula, gives 68 degrees F; and multiplying by 5/9 instead of 9/5 gives about 55.6 + 32 = 87.6 degrees F.

Correct answer: 10 degrees C

Fifty degrees Fahrenheit equals 10 degrees C: 50 - 32 = 18, and 5/9 × 18 = 10. Stopping at 18 degrees C skips the multiplication by 5/9; adding 32 instead of subtracting it gives 5/9 × 82, about 45.6 degrees C; and multiplying 50 by 5/9 before subtracting 32 gives about 27.8 - 32 = -4.2 degrees C.

Correct answer: 98.6 degrees F

Thirty-seven degrees Celsius equals 98.6 degrees F, normal body temperature: 9/5 × 37 = 66.6, and 66.6 + 32 = 98.6. Stopping before adding 32 gives 66.6 degrees F; adding 32 to 37 without multiplying gives 69 degrees F; and subtracting 32 instead of adding it gives 34.6 degrees F.

Correct answer: 2 tablets

Give 2 tablets: the ordered 500 mg divided by 250 mg per tablet is 2. Dividing the tablet strength by the order (250 ÷ 500) gives 0.5 tablets; misreading the 250 mg tablet as 25 mg gives 500 ÷ 25 = 20 tablets; and inverting the division while also misreading the 500 mg order as 50 mg, 250 ÷ 50, gives 5 tablets.

Correct answer: 2 mL

The volume needed is 2 mL: 40 mg ÷ 100 mg × 5 mL = 2 mL. Dividing the 40 mg dose by the 5 mL volume gives 8 mL; dividing 40 by 100 without multiplying by the 5 mL gives 0.4 mL; and inverting that ratio, 100 ÷ 40 with no 5 mL, gives 2.5 mL.

Correct answer: 2 tablets

Give 2 tablets: 0.25 mg ÷ 0.125 mg = 2. Dividing the tablet strength by the order (0.125 ÷ 0.25) gives 0.5 tablets; misreading the 0.125 mg tablet as 1.25 mg gives 0.25 ÷ 1.25 = 0.2 tablets; and making both slips, 1.25 ÷ 0.25, gives 5 tablets.

Correct answer: 300 mg

The total dose is 300 mg: 5 mg per kilogram × 60 kg = 300 mg. Dividing 60 by 5 gives 12 mg; dropping a zero (5 × 6) gives 30 mg; and treating the 60 kg as pounds, converting it to about 27.3 kg and multiplying by 5, gives about 136 mg.

Correct answer: 100 mg

There are 100 mg in 4 mL: 250 mg per 10 mL is 25 mg per mL, and 25 × 4 = 100. Multiplying 250 by 4 without dividing by the 10 mL gives 1000 mg; dividing 250 by 4 gives 62.5 mg; and 25 mg is the amount in 1 mL, not in 4 mL.

Correct answer: 85

The average is 85: 80 + 90 + 70 + 100 = 340, and 340 ÷ 4 = 85. Dividing by 5, as if for a five-day week, gives 68; leaving Thursday's 100 out of the total but still dividing by 4 gives 240 ÷ 4 = 60; and 30 is the range (100 - 70), not the mean.

Correct answer: $50,000

Supplies receive $50,000: 25% is 0.25, and 0.25 × 200,000 = 50,000. Reading the 15% 'other' slice instead gives $30,000; dividing 200,000 by 25 instead of taking 25% of it gives $8,000; and writing 25% as 0.025 gives $5,000.

Correct answer: 3/8

Surgery holds 3/8 of the patients. The total is 12 + 18 + 30 + 20 = 80, and 30/80 reduces to 3/8. 9/40 is the Pediatrics share (18/80), not Surgery's. 3/5 compares Surgery with the other units combined (30 to 50), which is a ratio, not a fraction of the total. 1/4 is the Maternity share (20/80).

Correct answer: x + 12 = 30

The equation is x + 12 = 30: 'the sum of a number and 12' is x + 12, and 'is 30' sets that sum equal to 30. 12x = 30 reads the sum as a product; x + 30 = 12 swaps the 12 and the total of 30; and 30x = 12 makes both slips, a product with the 12 and the 30 swapped.

Correct answer: 3x - 5 = 16

The equation is 3x - 5 = 16: 'three times a number' is 3x, 'decreased by 5' subtracts 5 from that product, and 'equals 16' sets the result equal to 16. 5x - 3 = 16 swaps the 3 and the 5. 5 - 3x = 16 reverses the subtraction, but 'decreased by 5' takes 5 away from 3x. 3 - 5x = 16 swaps the numbers and also reverses the subtraction.

Correct answer: x/4 = 9

The equation is x/4 = 9: 'a number divided by 4' is x/4, and 'gives 9' sets that quotient equal to 9. 4x = 9 multiplies instead of dividing; 4/x = 9 divides 4 by the number, reversing the order; and x - 4 = 9 subtracts instead of dividing.

Correct answer: 2(x + 3) = 18

The equation is 2(x + 3) = 18. "The sum of a number and 3" is x + 3, and "twice" that sum multiplies the whole expression by 2. 2x + 3 = 18 doubles only the number, not the sum. x + 3 = 2(18) doubles the 18 instead of the sum. 2 + (x + 3) = 18 adds 2 instead of multiplying by 2.

Correct answer: 5x = 40

The equation is 5x = 40: x hours a day for 5 days is 5 times x, and that total equals 40 hours. 40x = 5 swaps the total and the number of days; x/40 = 5 divides the daily hours by the total instead of multiplying by the days; and x + 5 = 40 adds the days instead of multiplying.

Correct answer: 14

The value is 14: the parentheses give 8 - 3 = 5, then 5 × 2 = 10 and 16 ÷ 4 = 4, and 10 + 4 = 14. Ignoring the parentheses gives 8 - 6 + 4 = 6; skipping the division and adding 16 to the 10 gives 26; and adding 2 to 16 ÷ 4 before multiplying by 5 gives 5 × 6 = 30.

Correct answer: 70%

The fraction 7/10 equals 70%: 7 ÷ 10 = 0.7, and multiplying by 100 gives 70%. Reading 7/10 as 7 hundredths gives 7%; 30% is the remaining 3/10, not 7/10; and dividing 10 by 7 instead of 7 by 10 gives about 143%.

Correct answer: 8 nurses

The unit needs 8 nurses: one nurse for every 6 patients means 48 ÷ 6 = 8. Subtracting 6 from 48 gives 42 nurses; 6 nurses copies the 6 patients per nurse instead of dividing by it; and dividing 48 by 7, as if the 1 and the 6 made a group of 7 that the 48 must be split into, gives about 7 nurses.

Correct answer: 3 tablets

Give 3 tablets: 600 mg ÷ 200 mg per tablet = 3. Dividing the tablet strength by the order (200 ÷ 600) gives 0.33 tablets; dividing 600 by 100, as if each tablet held 100 mg, gives 6 tablets; and inverting the division while also misreading the 200 mg tablet as 20 mg, 20 ÷ 600, gives 0.03 tablets.

Correct answer: 30

The value is 30. Work inside the parentheses first (3 + 6 = 9), then the exponent (2³ = 8), then the division (18 ÷ 9 = 2), and finally add and subtract from left to right: 24 - 2 + 8 = 30. An answer of 28 comes from treating 2³ as 2 × 3 = 6, giving 24 - 2 + 6. An answer of 23 comes from splitting the division across the sum, 18 ÷ 3 + 18 ÷ 6 = 9, giving 24 - 9 + 8. An answer of 21 makes both of those mistakes: 24 - 9 + 6.

Correct answer: 21

The sum is 21: √(144) = 12 because 12 × 12 = 144, and √(81) = 9 because 9 × 9 = 81, so 12 + 9 = 21. An answer of 15 comes from adding first and then taking one square root, √(144 + 81) = √(225); square roots cannot be combined that way. An answer of 108 multiplies the roots, 12 × 9, instead of adding them. An answer of 225 adds 144 and 81 but forgets to take the square roots at all.

Correct answer: 7,500

Rounded to the nearest hundred, 7,468 is 7,500: the digit after the hundreds place is 6, which is 5 or more, so the hundreds digit rounds up from 4 to 5 and the digits after it become zeros. An answer of 7,400 simply drops the last two digits instead of rounding. An answer of 7,470 rounds to the nearest ten instead of the nearest hundred. An answer of 8,000 keeps rounding in a chain (7,468 to 7,470 to 7,500 to 8,000) and ends at the nearest thousand instead of the nearest hundred.

Correct answer: 10

The value is 10. Subtracting a negative is the same as adding a positive, so the expression becomes -8 + 15 + 3; then -8 + 15 = 7 and 7 + 3 = 10. An answer of 4 treats - (-3) as - 3, giving 7 - 3. An answer of -4 gives -8 + 15 the sign of the first number, -7, and then adds 3. An answer of -20 applies the first negative sign to the whole sum, -(8 + 15) = -23, and then adds 3.

Correct answer: 42

The product is 42. Multiplying two negative numbers gives a positive result, and 6 × 7 = 42, so -6 × -7 = 42. An answer of -42 applies the sign rule wrongly, as if a negative times a negative stayed negative. An answer of -13 adds instead of multiplying: -6 + (-7) = -13. An answer of 13 makes both mistakes: it adds 6 and 7 instead of multiplying, then gives the sum a positive sign because both numbers were negative.

Correct answer: 108

The area is 108 square feet, because the area of a rectangle is length × width and 12 × 9 = 108. An answer of 42 is the perimeter, 2 × (12 + 9), which measures the distance around the room rather than the floor it covers. An answer of 21 adds the length and the width, 12 + 9, instead of multiplying them. An answer of 144 squares the length, 12 × 12, as if the room were a square 12 feet on each side.

Correct answer: 40

The perimeter is 40 centimeters: perimeter = 2 × (length + width) = 2 × (14 + 6) = 2 × 20 = 40. An answer of 84 is the area, 14 × 6, which measures the surface inside the rectangle rather than the distance around it. An answer of 56 uses the square rule, 4 × 14, as if all four sides were 14 centimeters long. An answer of 168 mixes up the formulas and uses 2 × length × width, 2 × 14 × 6.

Correct answer: 78.5

The area is 78.5 square centimeters: area = pi × radius², so 3.14 × 25 = 78.5. 15.7 multiplies pi by the radius without squaring it (3.14 × 5). 31.4 is the circumference (2 × 3.14 × 5), the distance around the bandage rather than its area. 314 uses the diameter, 10, in place of the radius (3.14 × 10 × 10).

Correct answer: 1,000

Rounding 49 to the nearest ten gives 50 and rounding 21 gives 20, so the estimate is 50 × 20 = 1,000. Multiplying the original numbers gives the exact product, 1,029, which is not an estimate. Rounding 21 up to 30 instead of down to 20 gives 50 × 30 = 1,500, and rounding only 49 while leaving 21 unchanged gives 50 × 21 = 1,050.

Correct answer: 2.65

Write 5.4 as 5.40 so the decimal points line up, then subtract: 5.40 - 2.75 = 2.65. Subtracting the smaller digit from the larger in each column instead of borrowing gives 3.35. Borrowing for the tenths place but forgetting to reduce the ones digit from 5 to 4 gives 3.65, and writing 5.4 as 5.04 gives 5.04 - 2.75 = 2.29.

Correct answer: 0.24

Multiply 6 by 4 to get 24. Each factor has one decimal place, so the product needs two decimal places: 0.24. 0.024 uses three decimal places, one too many. 2.4 uses only one decimal place. 1.0 is the sum, 0.6 + 0.4, not the product.

Correct answer: 5/8

Write 1/4 with the common denominator 8 as 2/8, then subtract: 7/8 - 2/8 = 5/8, which is already in lowest terms. Subtracting the numerators without first rewriting 1/4 in eighths gives (7 - 1)/8 = 6/8. Rewriting 1/4 as 4/8 by multiplying the numerator by 4 instead of 2 gives 7/8 - 4/8 = 3/8, and subtracting the numerators over the product of the denominators gives 6/32, which reduces to 3/16.

Correct answer: 14

Change 3 1/2 to the improper fraction 7/2, then multiply by the reciprocal of 1/4: 7/2 × 4/1 = 28/2 = 14. Converting 3 1/2 as 5/2 (multiplying the whole number by the numerator and adding the denominator) gives 5/2 × 4 = 10. Dividing only the whole number, 3 ÷ 1/4 = 12, drops the half, and multiplying by 1/4 instead of dividing gives 7/2 × 1/4 = 7/8.

Correct answer: 9

The range is the largest value minus the smallest value: 13 - 4 = 9. 10 comes from adding 1 to that difference, as if counting the whole numbers from 4 to 13. 8 is the mean (40 ÷ 5), which measures the center, not the spread. 7 is both the mode and the median, which are also measures of center.

Correct answer: 1/2

There are 5 blue chips among 3 + 5 + 2 = 10 chips, so the probability is 5/10, which reduces to 1/2. Treating the three colors as equally likely gives 1/3, which ignores how many chips of each color there are. Using one chip out of the ten gives 1/10, which counts a single blue chip, and 1/5 is the probability of drawing green (2/10), read from the wrong color.

Correct answer: 2.3 x 10^3

Moving the decimal point in 2,300 three places to the left gives 2.3, a number between 1 and 10, so the exponent is positive 3: 2.3 x 10^3. A negative exponent is used only for numbers smaller than 1, so 2.3 x 10^-3 equals 0.0023. Counting only the two zeros gives 2.3 x 10^2, which equals 230, and making both mistakes gives 2.3 x 10^-2, which equals 0.023.

Correct answer: 9

The mean is the total divided by the number of shifts: 8 + 12 + 10 + 6 = 36, and 36 ÷ 4 = 9 hours. Averaging only the first and last shifts listed, (8 + 6) ÷ 2, gives 7. Entering 8 + 12 + 10 + 6 ÷ 4 without grouping the sum divides only the last shift and gives 31.5, and stopping at the total, 36, without dividing by the 4 shifts gives the sum of the hours rather than the average.

Correct answer: 750

Total volume equals rate times time: 125 mL per hour × 6 hours = 750 mL. Working the multiplication digit by digit, 6 × 5 = 30 (write 0, carry 3), 6 × 2 + 3 = 15 (write 5, carry 1), and 6 × 1 + 1 = 7. Dropping the first carry gives 720, dropping the second carry gives 650, and dropping both carries gives 620.

Correct answer: The list of supplies is on the counter.

A verb agrees with its subject, not with a noun inside a prepositional phrase that follows the subject. Here the subject is the singular noun "list"; "of supplies" only describes it. So "The list of supplies is on the counter." is correct. "A list of supplies were on the counter." matches the plural "were" to "supplies" instead of "list." "A list of supplies are on the counter." makes the same mistake with "are." "The list of supplies sit on the counter." uses the plural "sit" where the singular subject needs "sits."

Correct answer: Are

When two subjects are joined by "neither ... nor," the verb agrees with the subject closer to it. In "Neither the doctor nor the nurses ___ available right now," the closer subject is the plural "nurses," so the plural verb "are" is correct. "Is" and "seems" are singular forms that agree with "doctor," the farther subject. "Was" is also singular, and its past tense clashes with "right now."

Correct answer: Each of the patients has a chart.

The pronoun "each" is singular, so it takes a singular verb even when a plural noun follows "of the." "Each of the patients has a chart." uses the singular "has." "Each of the patients have a chart." matches the verb to "patients" instead of to the real subject, "each." "Each of the patients own a chart." uses the plural "own" where the singular "owns" is needed. "Each of the patients get a chart." uses the plural "get" where the singular "gets" is needed.

Correct answer: There are several reasons for the delay.

When a sentence begins with "there," the word "there" is not the subject. The verb agrees with the noun that follows it. Here that noun is the plural "reasons," so "There are several reasons for the delay." is correct. "There is several reasons for the delay." puts the singular verb "is" with the plural "reasons." "There was several reasons for the delay." makes the same mistake with the singular "was." "There were several reason for the delay." has a plural verb but a singular noun: "several" needs "reasons," and "were" does not agree with "reason."

Correct answer: The team of researchers is celebrating its discovery.

A collective noun such as "team" takes a singular verb when the group acts as one unit, and the verb and the pronoun must both stay singular. "The team of researchers is celebrating its discovery." pairs the singular "team" with "is" and "its." "The team of researchers have announced its discovery." uses the plural "have" with the singular "its." "The team of researchers are celebrating its discovery." matches the plural "are" to "researchers" in the prepositional phrase. "The team of researchers were reporting its discovery." makes the same mismatch with "were."

Correct answer: Is

Some nouns end in "s" but name a single subject or field of study, and they take singular verbs. "Mathematics" is one of these, so the sentence reads "Mathematics is a required subject for nursing students." "Are" is a plural verb, so it treats "mathematics" as if it named several things. "Be" is the base form, which follows a helping verb ("must be") and cannot be the main verb right after a subject. "Were" is plural and also past tense, so it does not fit a requirement that is still in effect.

Correct answer: My favorite part of the lectures is the demonstrations.

A linking verb agrees with its subject, not with the noun that follows it or a noun in a prepositional phrase. The subject here is the singular "part," so "My favorite part of the lectures is the demonstrations." is correct even though "lectures" and "demonstrations" are plural. "My favorite part of the lecture are the demonstrations." pairs the singular subject "part" with the plural verb "are." "My favorite part of the lecture were the demonstrations." makes the same mistake with the plural "were." "My favorite parts of the lecture is the demonstrations." has the plural subject "parts" but keeps the singular verb "is."

Correct answer: Everybody in the classes was given a syllabus.

Indefinite pronouns such as "everybody," "everyone," and "each" are singular and take singular verbs, even when a plural noun follows in a phrase. "Everybody in the classes was given a syllabus." uses the singular "was." "Everybody in the classes were given a syllabus." and "Everybody in the classes are given a syllabus." use plural verbs that agree with "classes" instead of the subject. "Everybody in the classes have been given a syllabus." makes the same error with "have been," where "has been" would agree.

Correct answer: After the long shift, the nurse finally rested.

A comma follows an introductory phrase to mark where it ends and the main clause begins, and no single comma should come between a subject and its verb. The introductory phrase is "After the long shift," so the comma goes right after "shift": "After the long shift, the nurse finally rested." "After the long shift the nurse, finally rested." leaves out the needed comma and puts one between the subject "nurse" and its verb. "After the long, shift the nurse finally rested." splits "long shift," two words that belong together. "After the long shift the nurse finally, rested." leaves out the needed comma and cuts the adverb "finally" off from the verb it modifies.

Correct answer: She packed bandages, gloves, a thermometer, and a notebook.

Commas separate the items in a series, and in Chicago style a comma also comes before the final "and" (the serial comma). No comma goes between a verb and its object. "She packed bandages, gloves, a thermometer, and a notebook." follows both rules. "She packed, bandages, gloves, a thermometer, and a notebook." puts a comma between the verb "packed" and the list it governs. "She packed bandages; gloves; a thermometer; and a notebook." uses semicolons. Semicolons are needed only when the items already contain commas, and these items do not. "She packed bandages gloves, a thermometer, and a notebook." leaves out the comma between the first two items, so "bandages gloves" reads as one item.

Correct answer: The patient's records were updated this morning.

An apostrophe shows possession; it never forms a plain plural. For one owner, add an apostrophe and "s" ("patient's"); for a plural owner ending in "s," add the apostrophe alone ("patients'"). "The patient's records were updated this morning." shows one patient owning the records, and the plural "records" takes no apostrophe. "The patients record's were updated this morning." drops the possessive apostrophe from "patients" and adds one to the plain plural "records." "The patients' record's were updated this morning." has a correct plural possessive but the same wrong apostrophe in "record's." "The patients's records were updated this morning." adds "'s" to a plural that already ends in "s," where only the apostrophe belongs.

Correct answer: The schedule changed; however, no one was notified.

"However" is a conjunctive adverb, not a conjunction, so it cannot join two independent clauses with commas alone. Put a semicolon before it and a comma after it: "The schedule changed; however, no one was notified." "The schedule changed, however, no one was notified." is a comma splice, because two complete clauses are joined only by commas. "The schedule changed; however; no one was notified." uses a second semicolon after "however," where a comma belongs, so "however" is cut off as if it were a clause of its own. "The schedule changed; however, no one, was notified." punctuates "however" correctly but adds a comma between the subject "no one" and its verb "was notified."

Correct answer: Dr. Reyes, who runs the clinic, approved the plan.

A nonessential clause adds extra information that the sentence could do without, so it is set off with a comma on both sides, like a pair of parentheses. "Dr. Reyes, who runs the clinic, approved the plan." encloses "who runs the clinic" in a pair of commas. "Dr. Reyes, who runs the clinic approved the plan." opens the clause but never closes it. "Dr. Reyes who runs the clinic, approved the plan." closes it but never opens it, leaving a lone comma between the subject and the verb. "Dr. Reyes, who runs the clinic approved, the plan." misplaces the closing comma after "approved," which cuts the verb off from its object.

Correct answer: The instructor said, "Wash your hands before each visit."

In US style, a quoted full sentence follows a comma after the verb of speaking, begins with a capital letter, and puts the final period inside the closing quotation mark. 'The instructor said, "Wash your hands before each visit."' follows all three rules. 'The instructor, said "Wash your hands before each visit."' puts the comma between the subject and the verb instead of before the quotation. 'The instructor said, "wash your hands before each visit."' starts the quoted sentence with a lowercase letter. 'The instructor said, "Wash your hands before each visit".' puts the period outside the closing quotation mark, which US style does not allow.

Correct answer: The nurse charted the results.

A complete sentence needs a subject, a main (finite) verb, and a complete thought. "The nurse charted the results." has the subject "nurse," the verb "charted," and stands on its own. "Because the medication arrived late." has a subject and verb, but the word "because" makes it a dependent clause that leaves the thought unfinished. "The doctor reviewing the new scans." has a subject, but "reviewing" is a participle, not a main verb; it would need "is" or "was" to work. "After the morning rounds." is a prepositional phrase with no subject or verb at all.

Correct answer: The alarm sounded; everyone left the building.

The run-on contains two independent clauses, "The alarm sounded" and "everyone left the building." A semicolon can join two closely related independent clauses, and it must sit exactly where the first clause ends: "The alarm sounded; everyone left the building." "The alarm sounded, everyone left the building." uses a comma alone, which creates a comma splice. "The alarm sounded everyone; left the building." splits the subject "everyone" from its verb "left" and still runs "sounded" into "everyone." "The alarm sounded everyone left, the building." leaves the two clauses fused and puts a comma between the verb "left" and its object, "the building."

Correct answer: The patient rested the family waited nearby.

A run-on (fused sentence) joins two independent clauses with no punctuation or connecting word between them. "The patient rested the family waited nearby." runs "The patient rested" straight into "the family waited nearby," so it is the sentence that needs correction. The other three are correct: "The patient rested, and the family waited nearby." joins the clauses with a comma and the conjunction "and"; "While the patient rested, the family waited nearby." turns the first clause into a dependent clause with "while"; and "The patient rested; the family waited nearby." joins them with a semicolon.

Correct answer: Maria studied for the entrance exam every evening.

A fragment becomes a sentence only when it has a subject and a main (finite) verb that are not trapped in a dependent clause. "Maria studied for the entrance exam every evening." supplies the subject "Maria" and the past-tense verb "studied." "Maria, who studied for the entrance exam every evening." puts the verb inside a relative clause, so "Maria" never gets a main verb. "Studying for the entrance exam every evening at home." only adds another phrase, so it still has no subject or main verb. "Because she studied for her exam every evening." is a dependent clause that cannot stand alone.

Correct answer: The results were ready, so the doctor reviewed them at once.

One way to fix a comma splice is to add a coordinating conjunction (and, but, or, so, for, nor, yet) after the comma. "The results were ready, so the doctor reviewed them at once." does this with "so." "The results were ready, then the doctor reviewed them at once." uses "then," which is an adverb rather than a conjunction, so the comma splice remains. "The results were ready so, the doctor reviewed them at once." puts the comma after "so" instead of before it. "The results were ready, thus the doctor reviewed them at once." uses the conjunctive adverb "thus," which needs a semicolon before it, not a comma.

Correct answer: Each student must bring his or her own calculator.

A pronoun must match its antecedent in number and take the case its job in the sentence requires. "Each student must bring his or her own calculator." uses the singular possessive "his or her" to match the singular "each student." "Between you and I, the final exam was easier than we expected." uses the subject form "I" as the object of the preposition "between"; it should be "between you and me." "The charge nurse thanked Lena and myself for the help." uses the reflexive "myself" with no "I" earlier in the sentence for it to reflect; it should be "me." "Us students must bring our badges to class." uses the object form "us" as part of the subject; it should be "we students."

Correct answer: The supervisor gave the new badges to Maria and me.

A pronoun that is the object of a preposition takes the objective case (me, him, her, us, them). Here both "Maria" and the pronoun are objects of "to," so "The supervisor gave the new badges to Maria and me." is correct; dropping "Maria" shows it, since "gave the badges to me" sounds right. "The supervisor gave the new badges to Maria and I." uses the subject form "I" ("gave the badges to I"). "The supervisor gave the new badges to Maria and myself." uses the reflexive "myself," which needs "I" as the subject of the same sentence. "The supervisor gave the new badges to Maria and she." uses the subject form "she" where the object form "her" would be needed.

Correct answer: The hospital updated its visiting policy.

A pronoun must agree in number with its antecedent: singular with singular, plural with plural. "The hospital updated its visiting policy." pairs the singular "hospital" with the singular "its." "The interns introduced himself to the unit." uses the singular reflexive "himself" for the plural "interns"; it should be "themselves." "The two surgeons reviewed his own notes." uses "his own," which must refer back to the subject, for the plural "two surgeons"; it should be "their own." "The clinics revised its own visiting rules." pairs the plural "clinics" with the singular "its"; it should be "their own."

Correct answer: When the technician calibrated the machine, the technician noted the reading.

A pronoun needs one clear antecedent. If two nouns could be meant, repeat or name the noun. "When the technician calibrated the machine, the technician noted the reading." repeats "the technician," so there is no doubt about who noted the reading. In "When the nurse paged the surgeon, she explained the patient's latest results." the pronoun "she" could mean the nurse or the surgeon. In "After the pharmacist phoned the doctor, he changed the dose for the patient." the pronoun "he" could mean the pharmacist or the doctor. In "When the therapist moved the walker beside the chair, it suddenly tipped over." the pronoun "it" could mean the walker or the chair.

Correct answer: Who is responsible for the night shift?

Use "who" (like "he" or "she") when the pronoun is the subject of a verb, and "whom" (like "him" or "her") when it is an object. Here the pronoun is the subject of "is," so "Who is responsible for the night shift?" is correct; the answer would be "She is responsible," not "Her is responsible." "Whose responsible for the night shift?" confuses the possessive "whose" with "who's" (who is) and leaves the sentence without a verb. "Whom's responsible for the night shift?" and "Whom is responsible for the night shift?" both use the object form "whom" as the subject of "is."

Correct answer: The nurse checked the chart and updated the records.

Verbs that describe actions in the same time frame should stay in the same tense. "The nurse checked the chart and updated the records." keeps both verbs, "checked" and "updated," in the past tense. "The nurse checks the chart and updated the records." shifts from present to past in the middle of the sentence. "The nurse will check the chart and updated the records." pairs the future "will check" with the past "updated." "The nurse checking the chart and updated the records." uses the participle "checking" with no helping verb, so the first action has no working verb at all.

Correct answer: As the patient described her symptoms, the doctor wrote notes.

Two actions happening at the same moment, linked by "as," should be in the same tense. "As the patient described her symptoms, the doctor wrote notes." puts both "described" and "wrote" in the past. "As the patient describes her symptoms, the doctor wrote notes." and "As the patient is describing her symptoms, the doctor wrote notes." set a present-tense action beside a past one. "As the patient will describe her symptoms, the doctor wrote notes." sets a future action beside a past one, which cannot both be happening "as" the other does.

Correct answer: Yesterday she reviewed the notes and passed the quiz.

A time expression such as "yesterday" fixes the action in the past, so every verb that describes it should be past tense. "Yesterday she reviewed the notes and passed the quiz." uses the past "reviewed" and "passed." "Yesterday she will review the notes and pass the quiz." uses the future, which contradicts "yesterday." "Yesterday she reviews the notes and passes the quiz." uses the present tense for a past event. "Yesterday she reviewed the notes and passes the quiz." starts in the past and then shifts to the present "passes."

Correct answer: The researcher gathered the data, then she analyzed it carefully.

The tense shift is fixed by putting the first verb in the same tense as "analyzed," the past. "The researcher gathered the data, then she analyzed it carefully." changes "gathers" to "gathered," so both actions are in the past. "The researcher gathers the data, then she analyzed it carefully." is the original sentence, with the shift from present to past still in place. "The researcher will gather the data, then she analyzed it carefully." creates a new shift, from future to past. "The researcher gathering the data, then she analyzed it carefully." replaces the verb with the participle "gathering," which leaves the first clause without a working verb. (In polished writing the two clauses would also be joined with "and then" or a semicolon, but the tense of "gathered" is the point being tested.)

Correct answer: The technician cleaned the boots covered in mud.

A modifier should sit next to the word it describes. The mud is on the boots, so "covered in mud" belongs right after "boots": "The technician cleaned the boots covered in mud." "Covered in mud, the technician cleaned the boots." puts the phrase next to "technician," so it now says the technician was the one covered in mud. "Covered in mud, cleaning the boots was hard." leaves the phrase dangling, since "cleaning" cannot be covered in mud and the boots are no longer the subject. "The technician cleaned the boots in the sink covered in mud." places the phrase after "sink," so it seems to describe the sink rather than the boots.

Correct answer: The nurse gave a pamphlet to the patient about diabetes that was new.

A misplaced modifier sits so far from the word it describes that it seems to describe something else. In "The nurse gave a pamphlet to the patient about diabetes that was new." the phrases "about diabetes" and "that was new" both belong to "pamphlet," but they follow "patient" and "diabetes," so the sentence seems to describe a patient about diabetes and diabetes that was new. The other three place each modifier correctly: in "The aide brought the patient a blanket that had just been washed." the clause "that had just been washed" sits beside "blanket"; in "Smiling warmly, the nurse greeted the patient who was waiting nearby." the opening phrase describes "the nurse" and "who was waiting nearby" follows "patient"; and in "The aide handed the chart about the patient to the doctor who needed it." the phrase "about the patient" follows "chart" and the clause "who needed it" follows "doctor."

Correct answer: While the nurse was reading the chart, the phone rang loudly.

A dangling modifier has no logical subject in the sentence to describe, and here a phone cannot read a chart. The fix is to name the reader inside the modifier: "While the nurse was reading the chart, the phone rang loudly." "While reading the chart, the phone rang loudly for the nurse." mentions the nurse only at the end, so the phrase still attaches to "the phone." "Reading the chart, the nurse's own phone suddenly rang loudly." still makes "phone" the subject, and the possessive "nurse's" does not give the phrase a subject. "The phone rang loudly while reading through the nurse's chart." moves the phrase to the end, but "the phone" is still the only one doing the reading.

Correct answer: The student answered almost every question on the test.

A limiting modifier such as "almost," "only," or "nearly" applies to the word right after it, so it must sit directly before the word it limits. "The student answered almost every question on the test." places "almost" before "every question," meaning the student answered nearly all of them. "The student almost answered every question on the test." places it before "answered," so it says the student nearly answered but did not. "Almost the student answered every question on the test." and "The student answered every question almost on the test." attach "almost" to words it cannot sensibly limit, which leaves the meaning unclear.

Correct answer: The new policy will affect every department.

"Affect" is usually a verb meaning "to influence," while "effect" is usually a noun meaning "a result"; as a verb, "effect" means "to bring about" or "to create." "The new policy will affect every department." uses the verb "affect" correctly: the policy will influence every department. "The new policy will have an affect on every department." uses "affect" as a noun after "an," where the noun "effect" is needed. "The new policy will effect every department." uses the verb "effect," which would mean the policy will create every department. "The new policy will effect every department's budget." makes the same mistake, saying the policy will create each budget rather than influence it.

Correct answer: You should take the medication with food, not on an empty stomach.

Commonly confused words must be chosen by meaning, not sound. "You should take the medication with food, not on an empty stomach." uses every word correctly. "The clinic has been loosing patients to the new hospital across town." uses "loosing" (making something loose) where "losing" (failing to keep) is meant. "Their going to update the patient records tomorrow, after rounds." uses the possessive "their" where the contraction "they're" (they are) is needed. "After the exam, the doctor said the rash was worse then expected." uses "then," which refers to time, where "than," which makes a comparison, is needed.

Correct answer: It's almost time for the exam, and the room lost its key.

"It's" is always a contraction of "it is" or "it has"; "its," with no apostrophe, is the possessive form, like "his" or "her." "It's almost time for the exam, and the room lost its key." uses "it's" for "it is almost time" and "its" to show what belongs to the room. "Its almost time for the exam, and the room lost its key." drops the apostrophe the contraction needs. "It's almost time for the exam, and the room lost it's key." adds an apostrophe to the possessive, which would read "lost it is key." "Its almost time for the exam, and the room lost it's key." reverses both forms.

Correct answer: There were fewer complications than expected.

Use "fewer" with things that can be counted one by one and "less" with amounts that cannot be counted. Complications can be counted, so "There were fewer complications than expected." is correct. "There were less complications than expected." uses "less," which belongs with uncountable amounts such as "less pain." "There were lesser complications than expected." uses "lesser," which describes importance or rank ("a lesser concern") and is not followed by "than." "There were fewest complications than expected." uses the superlative "fewest," which compares three or more and cannot be followed by "than."

Correct answer: Please ensure the door is locked before you leave.

Only 'Please ensure the door is locked before you leave.' uses every word correctly: 'ensure' means to make certain, which is exactly the sense the sentence needs. 'We hope the drug has a strong affect on her pain.' uses the verb 'affect' where the noun 'effect' belongs after 'a strong'. 'The patient felt far worse then he had a week ago.' uses the time word 'then' where the comparison word 'than' is required. 'She could of finished the new intake form by noon.' writes 'could of', a mishearing of 'could have' (could've).

Correct answer: First, staff should wash their hands before and after each patient contact.

The best continuation is 'First, staff should wash their hands before and after each patient contact.' The opening promises several simple ways to prevent infection, and this sentence gives the first of them, signaled by 'First'. 'Next, staff should wipe down exam tables and chairs between patient visits.' is on topic, but 'Next' assumes an earlier step has already been given, and none has. 'In short, staff should follow these steps to keep every exam room spotless.' sums up steps that have not been listed yet. 'However, staff should also rest well and eat a full meal before each shift.' drifts from infection control to staff wellness and signals a contrast the paragraph does not need.

Correct answer: Studies show that people who work out regularly tend to fall asleep faster.

The best support is 'Studies show that people who work out regularly tend to fall asleep faster.' It offers evidence for the exact link the paragraph argues, that exercise leads to better sleep. 'Studies show that people who walk for exercise tend to have lower blood pressure.' supports a different benefit of exercise, heart health, not sleep. 'Studies show that hard workouts close to bedtime can delay sleep for some adults.' points the other way, so it weakens the argument instead of developing it. 'Studies show that most adults need seven to nine hours of sleep each night.' is about sleep alone and says nothing about exercise.

Correct answer: The cafeteria recently added three new dessert choices.

The sentence to remove is 'The cafeteria recently added three new dessert choices.' It has nothing to do with the benefits of drinking water, which is the paragraph's focus. 'Staying hydrated helps the body keep a steady temperature.', 'The kidneys need plenty of water to filter wastes well.' and 'Drinking enough water can sharpen the mind and ease headaches.' each state a real benefit of drinking water, so all three belong in the paragraph.

Correct answer: Together, these three simple habits greatly cut the spread of disease.

The best conclusion is 'Together, these three simple habits greatly cut the spread of disease.' It gathers handwashing, masks and clean surfaces into one closing point that restates the paragraph's main idea. 'In the end, handwashing protects people far better than masks or surfaces.' ranks one habit above the others, a claim the paragraph never made, so it does not sum up all three. 'Next, vaccines add another strong layer of protection against illness.' opens a new point, which a concluding sentence should not do. 'Masks also come in many sizes, so each person can find a good fit.' is a minor detail about one habit, not a conclusion.

Correct answer: 2, 3, 4, 1

The logical order is '2, 3, 4, 1': 'First' wet your hands, 'Then' scrub with soap, 'Next' rinse the soap away, and 'Finally' dry them. '2, 4, 3, 1' mixes up 'Then' and 'Next', so the soap is rinsed away before anyone scrubs with it. '1, 2, 3, 4' simply follows the printed numbers, which puts drying, the 'Finally' step, first. '1, 2, 4, 3' makes both mistakes: it starts with drying and also rinses before scrubbing.

Correct answer: Consequently

The blank needs a cause-and-effect transition, so 'Consequently' fits: 'The patient followed every instruction carefully; consequently, her recovery went smoothly.' The smooth recovery is the result of following the instructions. 'Nevertheless' signals a contrast, as if the recovery went smoothly in spite of her care, which the sentence does not mean. 'Additionally' only adds a second fact and hides the link between the care and the result. 'For instance' introduces an example, but the recovery is not an example of following instructions.

Correct answer: In response, the clinic could schedule visits in shorter time slots.

The best opening is 'In response, the clinic could schedule visits in shorter time slots.' The phrase 'In response' looks back at the problem and turns the reader toward a fix, which is the shift the second paragraph must signal. 'For example, patients often wait more than an hour in the clinic lobby.' only illustrates the problem again. 'In addition, the clinic's parking lot fills up early in the day.' adds a second problem instead of a solution. 'Similarly, phone calls to the clinic often go unanswered during busy periods.' describes yet another, similar problem, so none of these three moves the passage from problem to solution.

Correct answer: At the end, once the reasons have been explained

The sentence belongs 'At the end, once the reasons have been explained'. 'For these reasons' points back to reasons already given, so the sentence works as a closing statement. 'At the start, before the reasons have been explained' would leave 'these reasons' with nothing to refer to. 'In the middle, between the first two reasons' would close the argument while reasons are still to come. 'Right after the topic sentence, before any reasons are given' has the same problem as placing it first: no reasons have been stated yet.

Correct answer: The nurse, not the technicians, is responsible for the count.

The subject is "nurse"; a phrase set off by "not" does not change the subject, so the verb must be singular: "The nurse, not the technicians, is responsible for the count." The versions "The nurse, not the technicians, are responsible for the count." and "The nurse, not the technicians, were responsible for the count." make the verb agree with "technicians," the noun closest to it. "The nurse, not the technicians, have been responsible for the count." makes the same mistake with a plural helping verb; a singular subject needs "has been."

Correct answer: She gave a well-written report to the panel.

When two words work together as one adjective before a noun, they are joined with a hyphen: "She gave a well-written report to the panel." In "She gave a well written report to the panel." the hyphen is missing, so the two words do not read as a single modifier. "She gave a well-written-report to the panel." also hyphenates the noun, which is not part of the modifier, and "She gave a well written-report to the panel." puts the hyphen between the modifier and the noun instead of between the two parts of the modifier.

Correct answer: The nurse administered the medication.

In the active voice the subject performs the action: "The nurse administered the medication." has the nurse acting on the medication. "The medication was administered by the nurse." turns the receiver of the action into the subject and moves the doer into a "by" phrase, which is passive. "The medication had been administered carefully." and "The medication was being administered carefully." are also passive: each pairs a form of "be" with the past participle "administered," and neither says who acted.

Correct answer: The aide enjoys charting, lifting, and organizing supplies.

Items in a series must share one grammatical form, and after "enjoys" that form is the -ing form: "The aide enjoys charting, lifting, and organizing supplies." "The aide enjoys to chart, to lift, and organizing supplies." mixes two infinitives with an -ing word, and "The aide enjoys charting, to lift, and to organize supplies." mixes them the other way. "The aide enjoys charting, lifts, and organizing supplies." drops a present-tense verb, "lifts," into a list of -ing words.

Correct answer: Of the two thermometers, this one is more accurate.

When exactly two things are compared, use the comparative form. For a long adjective, that form is "more" plus the adjective: "Of the two thermometers, this one is more accurate." "Of the two thermometers, this one is most accurate." uses the superlative, which belongs to comparisons of three or more. "Of the two thermometers, this one is most accuratest." is a double superlative and also uses the wrong degree for two items. "Of the two thermometers, this one is more accurater." is a double comparative that adds an "-er" ending, which a long adjective like "accurate" does not take.

Correct answer: The patient did not have any complaints.

One negative is enough. "The patient did not have any complaints." pairs "not" with the neutral word "any." "The patient did not voice no complaints." combines "not" with "no," which is a double negative. "The patient wasn't making no complaints." makes the same error, because the contraction "wasn't" still contains "not." "The patient had scarcely no complaints." pairs "scarcely," which is itself a negative word, with "no."

Correct answer: The patient spoke with Doctor Lee about the results.

A title used directly before a name becomes part of the name and is capitalized, as is the surname: "The patient spoke with Doctor Lee about the results." "The patient spoke with doctor Lee about the Results." leaves the title lowercase and capitalizes the common noun "results." "The patient spoke with Doctor lee about the Results." leaves the surname lowercase and also capitalizes "results." "The patient spoke with doctor lee about the results." leaves both the title and the surname lowercase.

Correct answer: Because the room was full, we waited.

The single word "because" states the cause directly: "Because the room was full, we waited." "Due to the fact that the room was full, we waited." and "Owing to the fact that the room was full, we waited." each use a padded five-word phrase that means only "because," adding length without adding information. "Though the room was full, we waited." is just as short but changes the meaning, turning the cause into a contrast.

Correct answer: The role requires patience, skill, and dependability.

The list is parallel when all three items are nouns: "The role requires patience, skill, and dependability." "The role requires patience, to be skilled, and dependability." puts an infinitive phrase between two nouns, and "The role requires patience, skill, and to be dependable." ends the list of nouns with an infinitive. "The role requires patience, skilled, and dependable." follows a noun with two adjectives, which cannot serve as objects of "requires."

Correct answer: The patient waited for an hour in the lobby.

The choice between "a" and "an" depends on the first sound of the next word, and "hour" begins with a vowel sound because its "h" is silent: "The patient waited for an hour in the lobby." "The patient waited for a hour in the lobby." goes by the spelling instead of the sound. "The patient waited for an hours in the lobby." and "The patient waited for a hours in the lobby." pair a singular article with the plural "hours," which an article meaning "one" cannot introduce.

Correct answer: The samples should have gone to the lab already.

The helping verb "have" must be followed by a past participle, and the past participle of "go" is "gone": "The samples should have gone to the lab already." "The samples should have went to the lab already." uses the simple past "went," a common error with irregular verbs. "The samples should have going to the lab already." uses the -ing form, which follows "be," not "have," and "The samples should have goes to the lab already." uses the present-tense form.

Correct answer: The student answered the questions quickly.

A word that tells how an action was done modifies the verb, so it must be the adverb: "The student answered the questions quickly." "The student answered the questions quick." uses the adjective "quick" in place of the adverb. "The student answered the questions quickest." uses a superlative although nothing is being compared, and "The student answered the questions real quick." is informal; standard written English requires "quickly."

Correct answer: When a student studies daily, the student tends to feel more prepared.

The sentence opens in the third person with "a student," so the main clause must stay in the third person: "When a student studies daily, the student tends to feel more prepared." "When you study daily, the average learner tends to feel more prepared." simply moves the shift, starting in the second person and ending in the third. "When students study daily, you tend to feel more prepared." still shifts from the third-person "students" to the second-person "you," and "When a student studies daily, we tend to feel more prepared." shifts from the third person to the first-person "we."

Correct answer: Negative feedback stopping the response after balance is restored

This is 'Negative feedback stopping the response after balance is restored'. Rising glucose triggers insulin release, and the corrected glucose level then signals the pancreas to cut that release back, so the response does not overshoot. 'Positive feedback boosting the response until the stimulus ceases' would push glucose further from normal, the way contractions build during childbirth, instead of shutting the response off. 'Receptor downregulation lowering the response after long exposure' describes target cells losing receptors over weeks of high hormone levels, not insulin release falling within hours of a meal. 'Sensory adaptation dulling the response to an unchanging stimulus' describes receptors tuning out a constant stimulus, but here the stimulus itself, high glucose, was corrected.

Correct answer: Receptor, control center, effector, response

The functional order is 'Receptor, control center, effector, response'. A receptor senses the change, the control center compares it with the set point and sends a command, and the effector carries out the action that produces the response. 'Effector, control center, receptor, response' swaps the receptor and the effector, so the system would act before anything had sensed the change. 'Receptor, effector, control center, response' has the effector act before the control center has decided what to do. 'Effector, receptor, control center, response' makes both errors, starting with the effector and ending with the control center, so no command ever reaches the effector.

Correct answer: Set point

The target value is the 'Set point'. Homeostatic mechanisms keep blood pressure, glucose and temperature fluctuating within a narrow range around it. 'Threshold' is the level a stimulus must reach to trigger a response, such as firing an action potential, not the value the body tries to hold. 'Stimulus' is the change that disturbs the variable. 'Control center' is the structure, such as the hypothalamus, that compares the variable with the set point; it is not the value itself.

Correct answer: 100,000 times greater

The answer is '100,000 times greater'. Each pH unit is a tenfold change in hydrogen ion concentration, and pH 2 is five units below pH 7, so the factor is 10 to the fifth power, or 100,000, and the lower pH means more hydrogen ions. '100,000 times smaller' gets the factor right but reverses the direction: a lower pH number means a higher hydrogen ion concentration. '10,000 times greater' counts only four tenfold steps between 2 and 7 instead of five. '10,000 times smaller' makes both mistakes.

Correct answer: 0 to 14

The pH scale for aqueous solutions typically runs "0 to 14." A pH of 7 is neutral, values below 7 are acidic, and values above 7 are basic. "1 to 14" drops the bottom of the scale, although strong acids reach pH 0. "-7 to 7" wrongly makes neutral equal to zero. "0 to 10" cuts off the strongly basic range above 10.

Correct answer: pH 2

A strongly acidic sample is most consistent with 'pH 2'. Acids fall below 7, and the further below 7, the stronger the acid. 'pH 6' is on the acidic side but only weakly acidic, close to neutral. 'pH 12' reverses the scale: it is strongly basic, not strongly acidic. 'pH 8' is both on the wrong side of 7 and close to neutral, so it is only weakly basic.

Correct answer: Nucleus

The dense central core holding the protons and neutrons is the 'Nucleus', which contains nearly all of the atom's mass. 'Nucleolus' is a structure inside the nucleus of a cell, where ribosomes are made; it is not part of an atom. 'Electron cloud' is the region around the nucleus where the electrons are found. 'Energy level' is one of the shells that electrons occupy, again outside the nucleus.

Correct answer: A negative charge and a much smaller mass

An electron has 'A negative charge and a much smaller mass' than a proton: about 1/1836 of a proton's mass, so it adds almost nothing to an atom's mass. 'A positive charge and a much smaller mass' gets the mass right but gives the electron the proton's charge. 'A negative charge and a very similar mass' gets the charge right but treats the electron as heavy as a proton. 'A positive charge and a very similar mass' describes the proton itself, not the electron.

Correct answer: Share one or more pairs of electrons

In a covalent bond the atoms 'Share one or more pairs of electrons', so each atom can complete its outer shell. 'Transfer electrons to form ions of opposite charge' describes an ionic bond, in which the ions are held together by electrostatic attraction. 'Pool their electrons in a sea of electrons' describes metallic bonding, where electrons move freely among metal ions. 'Attract through temporary shifts of their electrons' describes London dispersion forces, weak attractions between molecules rather than a bond holding two atoms together.

Correct answer: Atomic number

The number of protons in the nucleus is the 'Atomic number'. It identifies the element and equals the number of electrons in a neutral atom. 'Mass number' counts protons plus neutrons, not protons alone. 'Oxidation number' is the charge an atom would carry if its bonds were fully ionic, and it changes from compound to compound. 'Quantum number' describes an electron's energy level and orbital, not the contents of the nucleus.

Correct answer: The cerebellum

Balance, posture and the fine timing of voluntary movements are coordinated by 'The cerebellum', which smooths motor activity so movements are not jerky. 'The cerebrum' starts voluntary movements and handles thought, memory and the senses, but it does not fine-tune coordination. 'The motor cortex' sends the commands that start voluntary movements, but it relies on the cerebellum to keep them balanced and well timed. 'The brainstem' relays signals and controls breathing and heart rate.

Correct answer: The brain and the spinal cord

The central nervous system is 'The brain and the spinal cord'. Every nerve and nerve cluster outside them belongs to the peripheral nervous system. 'The brain and the ganglia' wrongly counts the ganglia, clusters of nerve cell bodies outside the brain and spinal cord, as central. 'The cranial nerves and the spinal cord' swaps the brain for the cranial nerves, which branch off the brain and are peripheral. 'The cranial nerves and the ganglia' names two parts of the peripheral nervous system, the opposite division.

Correct answer: Involuntary functions such as heart rate and breathing

The medulla oblongata controls 'Involuntary functions such as heart rate and breathing', so damage there can stop these vital reflexes. 'Higher mental functions such as memory and reasoning' belong to the cerebrum. 'Motor functions such as balance and coordination' are handled by the cerebellum. 'Regulatory functions such as body temperature and thirst' are controlled by the hypothalamus, not the medulla.

Correct answer: Action potential

The rapid electrical signal that travels down an axon is an 'Action potential', also called a nerve impulse. It is an all-or-none event that keeps its full strength as it moves toward the axon terminal. 'Resting potential' is the steady voltage across the membrane of a neuron that is not firing, so it does not travel. 'Graded potential' is a small local change that fades with distance rather than racing down the axon. 'Postsynaptic potential' is a graded change in the receiving cell's membrane at a synapse, not the signal carried along the axon.

Correct answer: A gamete

The cell is 'A gamete', a sex cell such as a sperm or an egg. It is haploid, carrying half the usual number of chromosomes, so two gametes restore the full set at fertilization. 'A zygote' is the fertilized egg formed when two gametes join, so it already has the full diploid set. 'A somatic cell' is any ordinary body cell, which is diploid and is not passed to the next generation. 'A stem cell' is an unspecialized body cell that can divide and develop into other cell types, and it also carries the full set.

Correct answer: In the nucleus

DNA is primarily stored 'In the nucleus', the membrane-bound organelle that directs the cell's activities. 'In the lysosome' names a small sac of digestive enzymes that breaks down wastes, not a store of genetic material. 'In the ribosomes' confuses the place where proteins are built from the DNA's instructions with the place the DNA is kept. 'In the cell membrane' names the outer boundary that controls what enters and leaves the cell; it is made of lipids and proteins and holds no store of DNA.

Correct answer: Swell and possibly burst as water flows inward

The cell will 'Swell and possibly burst as water flows inward'. Distilled water is hypotonic to the cell, so water moves by osmosis toward the cell's higher solute concentration, and the cell can hemolyze. 'Shrink and possibly crenate as water flows outward' is what happens in a hypertonic solution, the reverse of this one. 'Keep its shape because pure water lacks solutes' misses the point: the missing solutes are exactly what draws water into the cell. 'Keep its shape because the membrane blocks water' is false, because the cell membrane lets water cross freely.

Correct answer: Ribosomes

The structures that read the genetic instructions and join amino acids into proteins are 'Ribosomes'. 'Lysosomes' break down worn-out parts and wastes with digestive enzymes; they do not build proteins. 'Nucleoli' make the parts that ribosomes are built from, but they do not assemble proteins themselves. 'Mitochondria' produce ATP for the cell's energy needs.

Correct answer: Reabsorption

Returning water, glucose and needed ions from the tubule to the blood is 'Reabsorption', which keeps valuable materials from being lost in the urine. 'Glomerular filtration' is the first step, when blood pressure forces fluid out of the glomerulus into the capsule; it moves substances out of the blood, not back into it. 'Tubular secretion' moves extra substances, such as hydrogen ions and some drugs, from the blood into the tubule. 'Micturition' is urination, the emptying of stored urine from the bladder, which happens long after the tubule has done its work.

Correct answer: Glomerulus

The tuft of capillaries where blood is first filtered is the 'Glomerulus', which sits inside the glomerular (Bowman's) capsule. 'Arteriole' names the small vessels that carry blood into and out of the glomerulus, not the filtering tuft itself. 'Vasa recta' are long, straight capillaries around the loop of Henle that help concentrate urine; no filtration happens there. 'Proximal tubule' is the first stretch of tubule after the capsule, where most reabsorption takes place.

Correct answer: Ureters

Urine travels from the kidneys to the bladder through the 'Ureters', two muscular tubes that move it along by peristalsis. 'Urethra' is the single tube that carries urine from the bladder out of the body, the step after storage. 'Renal veins' carry filtered blood, not urine, from the kidneys back toward the heart. 'Collecting ducts' lie inside the kidney and deliver urine to the renal pelvis, before it ever leaves the kidney.

Correct answer: Cytotoxic T cells

The cells that directly attack and destroy virus-infected body cells are 'Cytotoxic T cells', also called killer T cells. 'Helper T lymphocytes' coordinate the immune response by signaling other cells, but they do not kill infected cells themselves. 'Memory B lymphocytes' wait to mount a faster antibody response the next time the same antigen appears. 'Plasma B cells' release antibodies into the blood and lymph; the antibodies tag pathogens, but the plasma cells do not attack infected cells directly.

Correct answer: Antigen

A foreign molecule that the immune system recognizes and responds to is an 'Antigen'. 'Antibody' is the protein that B cells make to bind antigens, so it is part of the response, not its trigger. 'Cytokine' is a signaling protein that immune cells release to talk to one another. 'Pathogen' is a whole disease-causing organism, such as a virus or bacterium; the immune system recognizes it by the antigens on its surface.

Correct answer: Frequent infections because immune defenses are weakened

Helper T cells activate B cells and cytotoxic T cells, so losing them leads to 'Frequent infections because immune defenses are weakened'. 'Autoimmune disease because immune cells attack healthy tissue' reverses the problem: autoimmunity is an overactive or misdirected response, not a weakened one. 'Easy bruising because blood clotting is slowed' would follow from a loss of platelets, which helper T cells do not regulate. 'Chronic fatigue because blood oxygen levels are low' would follow from a shortage of red blood cells, whose job is to carry oxygen.

Correct answer: Potassium ions

The major positively charged ions inside cells are 'Potassium ions', and their movement across the membrane is central to nerve and muscle signals. 'Sodium ions' are the major positive ions outside the cells, in plasma and interstitial fluid. 'Calcium ions' are kept at very low levels inside most cells, and calcium is stored mainly in bone. 'Magnesium ions' are also found inside cells, but in far smaller amounts than potassium, so magnesium is not the major intracellular cation.

Correct answer: About 60 percent

Water makes up 'About 60 percent' of the adult body, which is why fluid balance matters so much. 'About 40 percent' is the share held inside the cells alone, the intracellular fluid, not the total. 'About 75 percent' fits a newborn infant, whose body holds proportionally more water than an adult's. 'About 90 percent' is closer to the water content of blood plasma than of the whole body.

Correct answer: Intracellular fluid

The fluid inside the body's cells is 'Intracellular fluid', which holds about two-thirds of the body's water. 'Extracellular fluid' is all the fluid outside the cells. 'Transcellular fluid' is a small part of the extracellular fluid held in special spaces, such as cerebrospinal, synovial, and pleural fluid. 'Interstitial fluid' is the part of the extracellular fluid that bathes the cells in the tissue spaces.

Correct answer: More acidic, so its pH falls

Extra carbon dioxide makes the blood 'More acidic, so its pH falls'. Dissolved carbon dioxide forms carbonic acid, which releases hydrogen ions, and more hydrogen ions mean a lower pH. 'More basic, so its pH rises' reverses the chemistry, since losing carbon dioxide, as in hyperventilation, is what makes blood more basic. 'More acidic, so its pH rises' gets the acid right but misreads the scale, because a more acidic solution has a lower pH number. 'More basic, so its pH falls' is wrong twice: the blood does not become basic, and a basic shift would raise the pH.

Correct answer: Alkalosis

Blood that is too basic, with a pH above the normal range of about 7.35 to 7.45, is in alkalosis. Acidosis is the opposite condition, a pH below the normal range. Hypercapnia means too much carbon dioxide in the blood, which pushes the pH down toward acidosis rather than up. Ketoacidosis is a form of metabolic acidosis caused by ketone buildup, as in uncontrolled diabetes, so it also lowers the pH.

Correct answer: Carbon dioxide and bicarbonate

The lungs and kidneys regulate blood pH mainly through carbon dioxide and bicarbonate. The lungs adjust carbon dioxide (and so carbonic acid) by changing the rate and depth of breathing, and the kidneys adjust bicarbonate and excrete hydrogen ions. 'Oxygen and red blood cell count' describes oxygen delivery: the lungs load oxygen and the kidneys release erythropoietin, but neither process is how pH is controlled. 'Sodium chloride and body water' is how the kidneys regulate blood volume and pressure, not acid-base balance. 'Calcium and phosphate' are balanced by the kidneys with bone and parathyroid hormone, and the lungs play no part.

Correct answer: Left ventricle

The left ventricle is the most muscular chamber, because it pumps oxygen-rich blood into the aorta and out to the whole body against high pressure. The right ventricle also pumps, but only to the nearby lungs at low pressure, so its wall is much thinner. The right atrium receives oxygen-poor blood from the body, and the left atrium receives oxygen-rich blood from the lungs; both atria only push blood a short distance into the ventricles, so they have the thinnest walls.

Correct answer: Veins

Veins carry oxygen-poor blood from the body back toward the heart, and because their pressure is low they contain one-way valves that stop blood from flowing backward. Pulmonary arteries do carry oxygen-poor blood, but they carry it away from the heart to the lungs, not back toward it. Capillaries are thin-walled exchange vessels between arterioles and venules, and they have no valves. Lymph vessels do have valves and return fluid toward the heart, but they carry lymph, not blood.

Correct answer: Contraction and relaxation of the cardiac chambers

Each heartbeat counted in a heart rate is one cycle of 'contraction and relaxation of the cardiac chambers': the atria and ventricles squeeze to eject blood and then relax to refill. 'Inflation and deflation of the pulmonary alveoli' describes breathing, which is counted separately as the respiratory rate of about 12 to 20 breaths per minute. 'Secretion and breakdown of the thyroid hormones' can raise or lower the heart rate over time, but it is not the beat itself. 'Dilation and constriction of the peripheral arteries' changes blood pressure and blood flow, not the rhythm of the beats.

Correct answer: Cornea

The cornea is the clear, dome-shaped front surface of the eye, and it does most of the bending of incoming light. The lens also focuses light, but it sits behind the iris and pupil, so light reaches it only after passing through the cornea; it fine-tunes the focus rather than bending light first. The sclera is the tough white outer coat, which is not transparent. The retina lines the back of the eye and detects light rather than bending it.

Correct answer: Iris

The iris is the colored ring of muscle that widens or narrows the pupil, letting in less light in bright conditions and more in dim conditions. The pupil is the opening in the center of the iris; it changes size, but it is the iris that adjusts it, and the pupil itself looks black, not colored. The lens is the clear structure behind the pupil that focuses light. The choroid is a dark, blood-rich layer at the back of the eye that nourishes the retina; it does not control the pupil.

Correct answer: Touch (somatosensation)

Skin receptors for pressure, temperature, and pain belong to the general sense of touch (somatosensation), whose receptors are spread across the skin and body rather than packed into one organ. Hearing (audition) is a special sense: hair cells in the cochlea of the inner ear respond to sound waves, not to skin pressure. Taste (gustation) is a special sense based on taste buds of the tongue that detect dissolved chemicals. Balance (vestibular sense) is also a special sense, detected by the semicircular canals and other inner-ear structures that respond to head movement and position.

Correct answer: Diaphragm relaxes, so the chest cavity shrinks

Quiet exhalation is passive: the 'diaphragm relaxes, so the chest cavity shrinks', the stretched lungs recoil, pressure inside them rises above air pressure, and air flows out. 'Diaphragm contracts, so the chest cavity expands' describes inhalation, which draws air in. 'Abdominal muscles contract, so the lungs compress' describes forced exhalation, such as during coughing or hard exercise, not normal quiet breathing. 'Intercostal muscles contract, so the ribs rise' is also part of inhalation, because lifting the ribs enlarges the chest and pulls air in.

Correct answer: Trachea, then bronchi, then bronchioles, then alveoli

Air moves from larger to smaller passages: 'trachea, then bronchi, then bronchioles, then alveoli'. The trachea divides into the two main bronchi, the bronchi branch into tiny bronchioles, and the bronchioles end in the alveoli, the air sacs where gas exchange occurs. 'Trachea, then bronchioles, then bronchi, then alveoli' puts the small bronchioles before the larger bronchi they branch from. 'Trachea, then bronchi, then alveoli, then bronchioles' places the alveoli in the middle, but they are the dead ends of the airway, beyond the bronchioles. 'Trachea, then alveoli, then bronchi, then bronchioles' makes both mistakes, putting the air sacs first and the airways that lead to them last.

Correct answer: Pituitary gland

The pituitary gland is called the master gland because its hormones, such as TSH, ACTH, FSH, and LH, direct the thyroid, adrenal glands, and gonads. The parathyroid gland controls blood calcium with parathyroid hormone but does not direct other glands. The adrenal gland releases cortisol, aldosterone, and epinephrine, and is itself directed by the pituitary through ACTH. The pineal gland secretes melatonin to help regulate sleep-wake cycles; it does not control other endocrine glands.

Correct answer: Receptors that recognize and bind the hormone

A hormone affects only target cells that have "receptors that recognize and bind the hormone." Cells without a matching receptor do not respond, even when the hormone reaches them. "Enzymes that break down and clear the hormone" describe how hormone signals end, mainly in the liver and kidneys; they do not decide which cells respond. "Glands that synthesize and secrete the hormone" are the endocrine cells that make the hormone, not the cells it acts on. "Capillaries that carry and deliver the hormone" cannot be the reason, because blood carries a hormone to nearly every cell in the body.

Correct answer: Antidiuretic hormone (ADH)

Antidiuretic hormone (ADH), released from the posterior pituitary, signals the kidney's collecting ducts to reabsorb more water, so less urine is produced and body water is conserved. Parathyroid hormone (PTH) acts on the kidneys too, but it makes them reabsorb calcium, not water. Growth hormone (GH) stimulates growth and metabolism and does not direct the kidneys to save water. Atrial natriuretic hormone (ANH), released by the heart when blood volume is high, does the opposite of conserving water: it makes the kidneys excrete more sodium and water.

Correct answer: Control group

The plants given no fertilizer are the control group: they are treated the same in every other way, so they show what growth looks like without the treatment. The experimental group is the set of plants that does receive the fertilizer. The independent variable is the factor the scientist changes, whether fertilizer is given, not a group of plants. The dependent variable is what she measures as the result, the amount of plant growth.

Correct answer: Controlled variables

Factors kept the same in every group so they cannot affect the outcome are controlled variables, also called constants. Dependent variables are the outcomes being measured, which are expected to change. Independent variables are the factors deliberately changed by the experimenter. Confounding variables are the opposite of controlled ones: they are uncontrolled factors that vary along with the treatment and distort the results, which is exactly what holding conditions constant is meant to prevent.

Correct answer: Liver

The liver makes bile, whose bile salts emulsify large fat globules into small droplets that digestive enzymes can attack. The gallbladder only stores and concentrates bile made by the liver and releases it after a fatty meal; it does not produce it. The pancreas releases lipase and other digestive enzymes into the small intestine, but not bile. The duodenum, the first part of the small intestine, is where bile is delivered and does its work, but it does not make bile.

Correct answer: Reabsorb water and form solid waste

A main job of the large intestine is to 'reabsorb water and form solid waste': as leftover material moves through the colon, water and electrolytes are reclaimed and the rest is compacted into feces. 'Absorb most nutrients and finish digestion' describes the small intestine, where nearly all nutrient absorption takes place. 'Produce bile and emulsify dietary fats' describes the liver, whose bile acts in the small intestine. 'Produce acid and begin protein digestion' describes the stomach, which secretes hydrochloric acid and pepsin.

Correct answer: Prompts the behavior needed to replace lost body fluid

Thirst is homeostatic because it 'prompts the behavior needed to replace lost body fluid': drinking corrects the deficit and returns body water toward its set point, a negative feedback response. 'Amplifies the loss of body fluid as positive feedback would' is backward, because thirst opposes the change rather than strengthening it. 'Signals the kidneys to conserve body fluid and concentrate urine' describes antidiuretic hormone, a separate response to dehydration; thirst is a sensation that acts through behavior, not a signal to the kidneys. 'Shifts body fluid out of the cells to refill the blood' describes water moving by osmosis between fluid compartments, which happens without thirst and does not add any new water to the body.

Correct answer: Enzymes

Enzymes are protein catalysts: they lower the energy needed to start a reaction, so it runs faster, and they are not used up. Antibodies are also proteins, but they bind antigens to fight infection rather than speed up reactions. Substrates are the molecules an enzyme acts on, and they are changed and used up in the reaction. Buffers are substances that resist changes in pH; they do not speed up reactions.

Correct answer: Denaturation

Denaturation is the unfolding of a protein when heat or extreme pH breaks the bonds that hold its three-dimensional shape; the active site is lost and the enzyme stops working. Inhibition slows an enzyme when another molecule binds to it, without heat or acid destroying its shape. Neutralization is the reaction of an acid with a base to form water and a salt, and a mutation is a change in the DNA sequence, not a change caused by temperature or pH.

Correct answer: ATP

ATP (adenosine triphosphate) is the molecule that cellular respiration makes to store usable energy, and cells break its last phosphate bond to power their work. ADP (adenosine diphosphate) is what is left after ATP gives up a phosphate; respiration adds a phosphate back to ADP to make ATP. AMP (adenosine monophosphate) has only one phosphate and is lower in energy still, and DNA stores genetic information rather than energy.

Correct answer: Anaerobic respiration

Anaerobic respiration, in the broad sense used here, breaks down glucose without oxygen; in muscle cells the pathway is anaerobic glycolysis, which yields only a little ATP and ends in lactic acid fermentation. Aerobic respiration needs oxygen to break glucose down completely, which is the very thing the oxygen-starved cell lacks. The electron transport chain is the final stage of aerobic respiration and depends on oxygen as the last electron acceptor. Passive transport moves substances across a membrane down their concentration gradient; it does not break down glucose or release energy.

Correct answer: Mitosis

Mitosis divides one body cell into two daughter cells with the same full set of chromosomes, which is how tissues grow and repair themselves. Meiosis produces sex cells with half the chromosome number, and its products are not identical. Cytokinesis is only the splitting of the cytoplasm at the end of a division, not a type of cell division in its own right. Apoptosis is programmed cell death, which removes cells rather than producing new ones.

Correct answer: Guanine

In DNA, cytosine always pairs with guanine, held by three hydrogen bonds, just as adenine pairs with thymine. Uracil is found in RNA, where it takes the place of thymine; it is not a DNA base. Adenine and thymine pair with each other, so neither one pairs with cytosine.

Correct answer: Genotype

The genotype is the pair of alleles an individual actually carries for a trait, such as one dominant and one recessive allele. The phenotype is the trait that can be observed, which may hide a recessive allele the person still carries. A karyotype is a picture of a cell's full set of chromosomes, arranged by size, not the alleles for one trait. An allele is a single version of a gene, so it is only one half of the pair that makes up the genotype.

Correct answer: Bone marrow

Red bone marrow, the soft tissue that fills the cavities of certain bones, produces red blood cells, white blood cells, and platelets, so bone marrow is the answer. Spongy bone is the hard, lattice-like bone tissue whose spaces hold the marrow; it is not itself the soft tissue that makes blood cells. Articular cartilage covers the ends of bones inside a joint and makes no blood cells, and the articular capsule encloses the joint; it does not form blood cells either.

Correct answer: Smooth muscle

Smooth muscle lines the walls of hollow organs such as the stomach and intestines and of blood vessels, and it contracts without conscious control. Skeletal muscle is attached to bones and is moved voluntarily. Cardiac muscle is also involuntary, but it is found only in the wall of the heart. Striated muscle is the striped type, which includes skeletal and cardiac muscle; the muscle in the gut and vessel walls has no striations.