1单选题A worldwide ban on the production of certain ozone-destroying chemicals would provide only an illusion of protection. Quantities of such chemicals, already produced, exist as coolants in millions of refrigerators. When they reach the ozone layer in the atmosphere, their action cannot be halted. So there is no way to prevent these chemicals from damaging the ozone layer further. Which of the following, if true, most seriously weakens the argument above?

2单选题Do you think cream cheese is too rich and luxurious to use as an everyday spread? Think again! Measure for measure, cream cheese has half the calories of butter. Indulge yourself with a clear conscience. The advertisement above is potentially misleading if which of the following is true? (A) Even butter is expensive in comparison with spreads that are still less expensive, such as margarine. (B) When using cream cheese as a spread, people tend to use several times as much as when using butter. (C) Other brands of cream cheese are approximately equal in caloric content to the brand advertised. (D) Even apart from caloric content, people generally think of cream cheese as luxurious because of its smooth taste. (E) Butter and cream cheese each contain a nutrient that the other does not.

3单选题Our words are meaningless and cannot be distinguished from their opposites, as can be proved by an example. People think that they know the difference between the meanings of "bald" and "having hair." Suppose an average person twentyone years of age has N hairs on his or her head. We say that that person is not bald but has hair. But surely one hair less would make no difference, and a person with N-1 hairs on his or her head would be said to have hair. Suppose we kept on, with one hair less each time. The result would be the same. But what would be the difference between someone who had one hair and someone who had none? We call them both bald. Nowhere can we make a distinction between "bald" and "having hair." Which of the following statements best counters the argument above? (A) The word "bald" can be translated into other languages. (B) A word can have more than one meaning. (C) A word such as "cat" can be applied to several animals that differ in some respects. (D) Words can lack precision without being meaningless. (E) People cannot think clearly without using words.

4单选题The geese that gather at the pond of a large corporation create a hazard for executives who use the corporate helicopter, whose landing site is 40 feet away from the pond. To solve the problem, the corporation plans to import a large number of herding dogs to keep the geese away from the helicopter. Which of the following, if a realistic possibility, would cast the most serious doubt on the prospects for success of the corporation's plan?

5单选题Houses built during the last ten years have been found to contain indoor air pollution at levels that are, on average, much higher than the levels found in older houses. The reason air-pollution levels are higher in the newer houses is that many such houses are built near the sites of old waste dumps or where automobile emissions are heavy. Which of the following, if true, calls into question the explanation above?

6单选题Sedimentary rock hardens within the earth's crust as layers of matter accumulate and the pressure of the layers above converts the layers below into rock. One particular layer of sedimentary rock that contains an unusual amount of the element iridium has been presented as support for a theory that a meteorite collided with the earth some sixty million years ago. Meteorites are rich in iridium compared to the earth's crust, and geologists theorize that a meteorite's collision with the earth raised a huge cloud of iridium-laden dust. The dust, they say, eventually settled to earth where it combined with other matter, and as new layers accumulated above it, it formed a layer of iridium-rich rock. Which one of the following, if true, would counter the claim that the iridium-rich layer described in the passage is evidence for the meteorite collision theory? (A) The huge dust cloud described in the passage would have blocked the transmission of sunlight and lowered the earth's temperature. (B) A layer of sedimentary rock takes millions of years to harden. (C) Layers of sedimentary rock are used to determine the dates of prehistoric events whether or not they contain iridium. (D) Sixty million years ago there was a surge in volcanic activity in which the matter spewed from the volcanoes formed huge iridium-rich dust clouds. (E) The iridium deposit occurred at about the same time that many animal species became extinct and some scientists have theorized that mass dinosaur extinctions were caused by a meteorite collision.

7单选题How does a building contractor most readily prove compliance with the building codes governing new construction? By using those established technologies that the authors of the codes had in mind when setting specifications. This, unfortunately, means that there will never be any significant technological innovation within the industry. Which of the following, if true, casts the most serious doubt on the conclusion above?

8单选题The teacher of yoga said that he knows how good the yoga exercises feel and how beneficial they are to his mental and spiritual health. After all, he said, there must be something sound to any human practice that endures more than three thousand years of history. Which of the following, if true, is the strongest relevant objection to the argument the teacher makes on the basis of the time yoga has endured?

9单选题Nuclear fusion is a process whereby the nuclei of atoms are joined, or "fused," and in which energy is released. One of the by-products of fusion is helium-4 gas. A recent fusion experiment was conducted using "heavy" water contained in a sealed flask. The flask was, in turn, contained in an air-filled chamber designed to eliminate extraneous vibration. After the experiment, a measurable amount of helium-4 gas was found in the air of the chamber. The experimenters cited this evidence in support of their conclusion that fusion had been achieved. Which one of the following, if tree, would cast doubt on the experimenters' conclusion? (A) Helium 4 was not the only gas found in the experiment chamber. (B) When fusion is achieved, it normally produces several byproducts, including tritium and gamma rays. (C) The amount of helium 4 found in the chamber's air did not exceed the amount of helium 4 that is found in ordinary air. (D) Helium 4 gas rapidly breaks down, forming ordinary helium gas after a few hours. (E) Nuclear fusion reactions are characterized by the release of large amounts of heat.

10单选题In the United States in 1986, the average rate of violent crime in states with strict gun-control laws was 645 crimes per 100,000 persons—about 50 percent higher than the average rate in the eleven states where strict gun-control laws have never been passed. Thus one way to reduce violent crime is to repeal strict gun control laws. Which of the following, if true, would most weaken the argument above? (A) The annual rate of violent crime in states with strict guncontrol laws has decreased since the passage of those laws. (B) In states with strict gun-control laws, few individuals are prosecuted for violating such laws. (C) In states without strict gun-control laws, many individuals have had no formal training in the use of firearms. (D) The annual rate of nonviolent crime is lower in states with strict gun-control laws than in states without such laws. (E) Less than half of the individuals who reside in states without strict gun-control laws own a gun.

11单选题People often recall having felt chilled before the onset of a cold. This supports the hypothesis that colds are, at least sometimes, caused by becoming chilled; it is the chill that allows a rhino virus, if present, to infect a person. Which of the following, if true, most seriously weakens the force of the evidence cited above?

12单选题Persons imprisoned for violent street crimes often commit the same crimes again after being released. Persons imprisoned for white-collar crimes such as receiving bribes or embezzlement, however, typically do not, after being released, repeat the crimes for which they have been imprisoned. It is fair to conclude that imprisonment, while it often fails to change the behavior of violent street criminals, does succeed in making white-collar criminals unwilling to repeat their crimes. Which of the following, if true, would most seriously weaken the conclusion stated above? (A) Statistics show that persons convicted of committing white-collar crimes rarely have a prison record. (B) The percentage of those who commit white-collar crimes and are imprisoned for doing so is lower than the percentage of those who commit violent street crimes and are imprisoned for doing so. (C) White-collar criminals whose prison sentences are shortened return to criminal activities at a slightly higher rate than white-collar criminals who serve their full sentences. (D) Persons released from prison after white-collar crimes are seldom given high positions or access to other people's money. (E) Persons who commit violent street crimes seldom commit white-collar crimes, and vice versa.

13单选题A researcher studying drug addicts found that, on average, they tend to manipulate other people a great deal more than nonaddicts do. The researcher concluded that people who frequently manipulate other people are likely to become addicts. Which of the following, if true, most seriously weakens the researcher's conclusion? (A) After becoming addicted to drugs, drug addicts learn to manipulate other people as a way of obtaining drugs. (B) When they are imprisoned, drug addicts often use their ability to manipulate other people to obtain better living conditions. (C) Some nonaddicts manipulate other people more than some addicts do. (D) People who are likely to become addicts exhibit unusual behavior patterns other than frequent manipulation of other people. (E) The addicts that the researcher studied were often unsuccessful in obtaining what they wanted when they manipulated other people.

14单选题One way for people to cut back on oil use is to switch to other types of fuel. Because wood is a renewable resource and can always be kept in constant supply, the use of wood instead of oil for home heating would be one way to assure the availability of energy resources in the future. The argument above would be most seriously weakened if which of the following were true?

15单选题The number of people 85 or older in the United States started increasing dramatically during the last ten years. The good health care that these people enjoyed in the United States during their vulnerable childhood years is primarily responsible for this trend. Which of the following, if true, most seriously weakens the explanation above?

16单选题These days, everyone talks about being too busy. But all this busyness does not seem to result in things getting done. Just as many tasks are still left uncompleted, phone calls unreturned, and appointments missed as there were in the days before this outbreak of busyness. Therefore, people must not be as busy as they claim. Which one of the following, if true, would most seriously weaken the conclusion in the passage?

17单选题Although spinach is rich in calcium, it also contains large amounts of oxalic acid, a substance that greatly impedes calcium absorption by the body. Therefore, other calcium-containing foods must be eaten either instead of or in addition to spinach if a person is to be sure of getting enough calcium. Which of the following, if true, most seriously weakens the argument above? (A) Rice, which does not contain calcium, counteracts the effects of oxalic acid on calcium absorption. (B) Dairy products, which contain even more calcium than spinach does, are often eaten by people who eat spinach on a regular basis. (C) Neither the calcium nor the oxalic acid in spinach is destroyed when spinach is cooked. (D) Many leafy green vegetables other than spinach that are rich in calcium also contain high concentrations of oxalic acid. (E) Oxalic acid has little effect on the body's ability to absorb nutrients other than calcium.

18单选题Some anthropologists study modern-day societies of foragers in an effort to learn about our ancient ancestors who were also foragers. A flaw in this strategy is that forager societies are extremely varied. Indeed, any forager society with which anthropologists are familiar has had considerable contact with modern nonforager societies. Which of the following, if true, would most weaken the criticism made above of the anthropologists' strategy?

19单选题It is widely assumed that a museum is helped financially when a generous patron donates a potential exhibit. In truth, however, donated objects require storage space, which is not free, and routine conservation, which is rather expensive. Therefore, such gifts exacerbate rather than lighten the demands made on a museum's financial resources. Which of the following, if true, most seriously weakens the argument above? (A) To keep patrons well disposed, a museum will find it advisable to put at least some donated objects on exhibit rather than merely in storage. (B) The people who are most likely to donate valuable objects to a museum are also the people who are most likely to make cash gifts to it. (C) A museum cannot save money by resorting to cheap storage under less than adequate conditions, because so doing would drive up the cost of conservation. (D) Patrons expect a museum to keep donated objects in its possession rather than to raise cash by selling them. (E) Objects donated by a patron to a museum are often of such importance that the museum would be obliged to add them to its collection through purchase if necessary.

20单选题The proposal to hire ten new police officers in Middletown is quite foolish. There is sufficient funding to pay the salaries of the new officers, but not the salaries of additional court and prison employees to process the increased caseload of arrests and convictions that new officers usually generate. Which of the following, if true, will most seriously weaken the conclusion drawn above? (A) Studies have shown that an increase in a city's police force does not necessarily reduce crime. (B) When one major city increased its police force by 19 percent last year, there were 40 percent more arrests and 13 percent more convictions. (C) If funding for the new police officers' salaries is approved, support for other city services will have to be reduced during the next fiscal year. (D) In most United States cities, not all arrests result in convictions, and not all convictions result in prison terms. (E) Middletown's ratio of police officers to citizens has reached a level at which an increase in the number of officers will have a deterrent effect on crime.