The chemical adenosine is released by brain cells when those cells are active. Adenosine then binds to more and more sites on cells in certain areas of the brain, as the total amount released gradually increases during wakefulness. During sleep, the number of sites to which adenosine is bound decreases. Some researchers have hypothesized that it is the cumulative binding of adenosine to a large number of sites that causes the onset of sleep.

Which of the following, if true, provides the most support for the researchers' hypothesis?

Consumers planning to buy recreational equipment tend to buy higher quality, more expensive equipment when the economy is strong than when it is weak. Hill and Dale is a business that sells high-quality, expensive camping and hiking equipment in Boravia. Although all the signs are that Boravia's economy is now entering a period of sustained strength, the managers of the business do not expect a substantial increase in sales.

Which of the following, if true, would provide the strongest justification for the managers' judgment?

Lawmaker: Raising taxes is not the only means of reducing government debt. The government's stockpile of helium is worth 25 percent more, at current market prices, than the debt accumulated in acquiring and storing it. Therefore, by selling the helium, the government can not only pay off that debt but reduce its overall debt as well.

Which of the following is an assumption on which the argument depends?

People who have spent a lot of time in contact with animals often develop animal-induced allergies, some of them quite serious. In a survey of current employees in major zoos, about 30 percent had animal-induced allergies. Based on this sample, experts conclude that among members of the general population who have spent a similarly large amount of time in close contact with animals, the percentage with animal-induced allergies is not 30 percent but substantially more.

Which of the following, if true, provides the strongest grounds for the experts' conclusion?

People who have spent a lot of time in contact with animals often develop animal-induced allergies, a significant percentage of which are quite serious. In a survey of current employees in major zoos, about 30 percent had animal-induced allergies. However, a zoo employee who develops a serious animal-induced allergy is very likely to switch to some other occupation.

Which of the following hypotheses receives the strongest support from the information given?

In order to raise revenue, the federal government planned a tax amnesty program that allows tax delinquents to pay all owed tax without added financial penalty. However, economists projected that the federal government would collect a far lower percentage of total tax owed by delinquents than did state governments implementing similar programs.

Which of the following, if true, would most contribute to an explanation of the economists' projections?

Which of the following, if true, provides evidence that most logically completes the argument below?

According to a widely held economic hypothesis, imposing strict environmental regulations reduces economic growth. This hypothesis is undermined by the fact that the states with the strictest environmental regulations also have the highest economic growth. This fact does not show that environmental regulations promote growth, however, since ______.

Each year red-winged blackbirds stop in a certain region of Midland Province on their spring and fall migrations. In the fall, they eat a significant portion of the province's sunflower crop. This year Midland farmers sought permits to set out small amounts of poisoned rice during the blackbirds' spring stop in order to reduce the fall blackbird population. Some residents voiced concern that the rice could threaten certain species of rare migratory birds. Nevertheless, the wildlife agency approved the permits.

Which of the following, if true, most helps to justify the wildlife agency's approval of the permits, given the concerns voiced by some residents?

A theory is either true or false. Galileo's observations of Jupiter's satellites showed that the Ptolemaic theory of the motion of celestial bodies is false. Therefore, since the Copernican theory of planetary motion is inconsistent with the Ptolemaic account, Galileo's observations of Jupiter's satellites proved the truth of the Copernican theory.

The argument above is open to the objection that it makes the questionable assumption that

Because mining and refining nickel is costly, researchers have developed an alternative method for extracting nickel using Streptanthus polygaloides, a plant that absorbs and stores nickel from the soil as it grows. The researchers incinerated a crop of Streptanthus they grew in nickel-rich soil. By chemically extracting nickel from the ash, they produced 100 pounds of nickel per acre of land at a total cost per pound slightly above that of current mining.

Which of the following, if true, most strongly supports the conclusion that the use of Streptanthus to extract nickel will be commercially adopted?

The milk of many mammals contains cannabinoids, substances that are known to stimulate certain receptors in the brain. To investigate the function of cannabinoids, researchers injected newborn mice with a chemical that is known to block cannabinoids from reaching their receptors in the brain. The injected mice showed far less interest in feeding than normal newborn mice do. Therefore, cannabinoids probably function to stimulate the appetite.

Which of the following is an assumption on which the argument depends?

Aroca City currently funds its public schools through taxes on property. In place of this system, the city plans to introduce a sales tax of three percent on all retail sales in the city. Critics protest that three percent of current retail sales falls short of the amount raised for schools by property taxes. The critics are correct on this point. Nevertheless, implementing the plan will probably not reduce the money going to Aroca's schools. Several large retailers have selected Aroca City as the site for huge new stores, and these are certain to draw large numbers of shoppers from neighboring municipalities, where sales are taxed at rates of six percent and more. In consequence, retail sales in Aroca City are bound to increase substantially.

In the argument given, the two potions in boldface play which of the following roles?

Business Consultant: Some corporations shun the use of executive titles because they fear that the use of titles indicating position in the corporation tends to inhibit communication up and down the corporate hierarchy. Since an executive who uses a title is treated with more respect by outsiders, however, use of a title can facilitate an executive's dealings with external businesses. Clearly, corporations should adopt the compromise of encouraging their executives to use their corporate titles externally but not internally, since even if it is widely known that the corporation's executives use titles outside their organization, this knowledge does not by itself inhibit communication within the corporation.

In the consultant's reasoning, the two portions in boldface play which of the following roles?

Several of a certain bank's top executives have recently been purchasing shares in their own bank. This activity has occasioned some surprise, since it is widely believed that the bank, carrying a large number of bad loans, is on the brink of collapse. Since the executives are well placed to know the bank's true condition, it might seem that their share purchases show that the danger of collapse is exaggerated. However, the available information about the bank's condition is from reliable and informed sources, and corporate executives do sometimes buy shares in their own company in a calculated attempt to calm worries about their company's condition. On balance, therefore, it is likely that the executives of the bank are following this example.

In the argument given, the two boldfaced portions play which of the following roles?

Which of the following most logically completes the argument below?

The expansion of large-scale farming in Africa and Asia has destroyed much of the natural vegetation on which elephants have historically depended, forcing them to turn to cultivated land to satisfy their enormous appetites. As a result, farmers have lost millions of dollars worth of crops annually. Yet even if elephant sanctuaries were created on a widespread basis to guarantee elephants sufficient natural vegetation, the raiding would likely persist, since