Critical Reasoning

Many athletes inhale pure oxygen after exercise in an attempt to increase muscular reabsorption of oxygen. Measured continuously after exercise, however, the blood lactate levels of athletes who inhale pure oxygen are practically identical, on average, to those of athletes who breathe normal air. The lower the blood lactate level is, the higher the muscular reabsorption of oxygen is. If the statements above are all true, they most strongly support which of the following conclusions?

Historian: Fifteenth-century advances in mapmaking contributed to the rise of modern nation-states. In medieval Europe (from the fifth to the fifteenth century), sovereignty centered in cities and towns and radiated outward, with boundaries often ambiguously defined. The conceptual shift toward the modern state began in the late fifteenth century, when mapmakers learned to reflect geography accurately by basing maps on latitude-longitude grids. By the mid-seventeenth century, nearly all maps showed boundary lines. Which of the following would, if true, most strengthen the historian’s reasoning?

Sascha: The attempt to ban parliament’s right to pass directed-spending bills—bills that contain provisions specifically funding the favorite projects of some powerful politicians—is antidemocratic. Our nation’s constitution requires that money be drawn from our treasury only when so stipulated by laws passed by parliament, the branch of government most directly representative of the citizens. This requirement is based on the belief that exercising the power to spend public resources involves the ultimate exercise of state authority and that therefore _________. Which of the following most logically completes Sascha’s argument?

Boreal owls range over a much larger area than do other owls of similar size. Scientists have hypothesized that **it is scarcity of prey that leads the owls to range so widely.** This hypothesis would be hard to confirm directly, since it is not possible to produce a sufficiently accurate count of the populations of small mammals inhabiting the forests where boreal owls live. Careful study of owl behavior has, however, shown that **boreal owls do range over larger areas when they live in regions where food of the sort eaten by small mammals is comparatively sparse.** This indicates that the scientists’ hypothesis is not sheer speculation. In the argument given, the two boldfaced portions play which of the following roles?

Cognitive scientist: Using the pioneering work of comparative psychologist Gordon Gallup as a model, several studies have investigated animals’ capacity for mirror self-recognition (MSR). Most animals exposed to a mirror respond only with social behavior, such as aggression. However, in the case of the great apes, repeated exposure to mirrors leads to self-directed behaviors, such as exploring the inside of the mouth, suggesting that these animals recognize the reflection as an image of self. The implication of these studies is that the great apes have a capacity for self-awareness unique among nonhuman species. The cognitive scientist makes which of the following assumptions in the argument above?

Last year a record number of new manufacturing jobs were created. Will this year bring another record? Well, any new manufacturing job is created either within an existing company or by the start-up of a new company. **Within existing firms, new jobs have been created this year at well below last year’s record pace.** At the same time, there is considerable evidence that the number of new companies starting up will be no higher this year than it was last year, and **there is no reason to think that the new companies starting up this year will create more jobs per company than did last year’s start-ups.** So clearly, the number of new jobs created this year will fall short of last year’s record. In the argument given, the two portions in boldface play which of the following roles?

A study of ticket sales at a summer theater festival found that people who bought tickets to individual plays had a no-show rate of less than 1 percent, while those who paid in advance for all ten plays being performed that summer had a no-show rate of nearly 30 percent. This may be at least in part because the greater the awareness customers retain about the cost of an item, the more likely they are to use it. Which of the following would, if true, best serve as an alternative explanation of the results of the study?

Although there is no record of poet Edmund Spenser’s parentage, we do know that as a youth, Spenser attended the Merchant Tailors’ School in London for a period between 1560 and 1570. Records from this time indicate that the Merchant Tailors’ Guild then had only three members named Spenser: Robert Spenser, listed as a gentleman; Nicholas Spenser, elected the Guild’s Warden in 1568; and John Spenser, listed as a “journeyman cloth-maker.” Of these, the last was likely the least affluent of the three—and most likely Edmund’s father, since school accounting records list Edmund as a scholar who attended the school at a reduced fee. Which of the following is an assumption on which the argument depends?

Hea Sook: One should not readily believe urban legends. Most legends are propagated because the moral lesson underlying them supports a political agenda. People will repeat a tale if it fits their purpose. They may not deliberately spread untruths, but neither are they particularly motivated to investigate deeply to determine if the tale they are telling is true. Kayla: But people would not repeat stories that they did not believe were true. Therefore, one can safely assume that if a story has been repeated by enough people, then it is more likely to be true. Kayla’s reply is most vulnerable to the criticism that it

Rainwater contains hydrogen of a heavy form called deuterium. The deuterium content of wood reflects the deuterium content of rainwater available to trees during their growth. Wood from trees that grew between 16,000 and 24,000 years ago in North America contains significantly more deuterium than wood from trees growing today. But water trapped in several North American caves that formed during that same early period contains significantly less deuterium than rainwater in North America contains today. Which of the following, if true, most helps to reconcile the two findings?

Enforcement of local speed limits through police monitoring has proven unsuccessful in the town of Ardane. In many nearby towns, speed humps (raised areas of pavement placed across residential streets, about 300 feet apart) have reduced traffic speeds on residential streets by 20 to 25 percent. In order to reduce traffic speed and thereby enhance safety in residential neighborhoods, Ardane’s transportation commission plans to install multiple speed humps in those neighborhoods. Which of the following, if true, identifies a potentially serious drawback to the plan for installing speed humps in Ardane?

NowNews, although still the most popular magazine covering cultural events in Kalopolis, has recently suffered a significant drop in advertising revenue because of falling circulation. Many readers have begun buying a competing magazine that, at 50 cents per copy, costs less than NowNews at $\$1.50$ per copy. In order to boost circulation and thus increase advertising revenue, NowNews’s publisher has proposed making it available at no charge. However, this proposal has a serious drawback, since __________. Which of the choices most logically completes the following argument?

Over the last five years, demand for hotel rooms in Cenopolis has increased significantly, as has the average price Cenopolis hotels charge for rooms. These trends are projected to continue for the next several years. In response to this economic forecast, Centennial Commercial, a real estate developer, is considering a plan to convert several unoccupied office buildings it owns in Cenopolis into hotels in order to maximize its revenues from these properties. Which of the following would it be most useful for Centennial Commercial to know in evaluating the plan it is considering?

Farmer: Several people in the past few years have claimed to have seen a mountain lion in the suburban outskirts—the latest just last month—and, while mountain lions were thought to have been driven from this entire region about twenty years ago, there is no reason for the people who reported seeing a mountain lion to have deliberately concocted a false report. Therefore, local wildlife managers should begin to urgently address the mountain lion’s presence. Which of the following would, if true, most seriously weaken the farmer’s argument?

The heavy traffic in Masana is a growing drain on the city’s economy—the clogging of the streets of the central business district alone cost the economy more than $\$1.2$ billion over the past year. In order to address this problem, officials plan to introduce congestion pricing, by which drivers would pay to enter the city’s most heavily trafficked areas during the busiest times of the day. Which of the following, if true, would most strongly indicate that the plan will be a success?

Economist: The most economically efficient way to reduce emissions of air pollutants is to tax them in proportion to the damage they are likely to cause. But in Country Y, many serious pollutants are untaxed and unregulated, and policy makers strongly oppose new taxes. Therefore, the best way to achieve a reduction in air pollutant emissions in Country Y would be to institute fixed upper limits on them. Which of the following is an assumption of the economist’s argument?

A study of high blood pressure treatments found certain meditation techniques and the most commonly prescribed drugs are equally effective if the selected treatment is followed as directed over the long term. Half the patients given drugs soon stop taking them regularly, whereas 80 percent of the study’s participants who were taught meditation techniques were still regularly using them five years later. Therefore, the meditation treatment is the one likely to produce the best results. Which of the following, if true, most seriously weakens the argument?

Many industrialized nations are trying to reduce atmospheric concentrations of carbon dioxide, a gas released by the burning of fossil fuels. One proposal is to replace conventional cement, which is made with calcium carbonate, by a new “eco-cement.” This new cement, made with magnesium carbonate, absorbs large amounts of carbon dioxide when exposed to the atmosphere. Therefore, using eco-cement for new concrete building projects will significantly help reduce atmospheric concentrations of carbon dioxide. Which of the following, if true, most strengthens the argument?

Professor: A marine biologist argues that transmission of sea lice from farm salmon to wild salmon is unlikely in the Broughton Archipelago, British Columbia, citing numerous studies suggesting that salinities less than 30 parts per thousand are unfavorable to sea-lice survival. The biologist concludes that the archipelago’s 25–30 parts per thousand salinity range between March and June, the critical period for wild salmon migration, tends to suppress sea-lice proliferation. But a review of the literature shows that salinities of 25–30 parts per thousand in combination with British Columbia’s cool spring temperatures favor the flourishing of sea lice. In this passage, the professor attempts to undermine the biologist’s argument by

Advertisement: When your car’s engine is running at its normal operating temperature, any major brand of motor oil will protect it about as well as Tuff does. When the engine is cold, it is a different story: Tuff motor oil flows better at lower temperatures than its major competitors do. So, if you want your car’s engine to have maximum protection, you should use Tuff. Which of the following, if true, most strengthens the argument in the advertisement?