Critical Reasoning

Only a reduction of 10 percent in the number of scheduled flights using Greentown’s airport will allow the delays that are so common there to be avoided. Hevelia airstrip, 40 miles away, would, if upgraded and expanded, be an attractive alternative for fully 20 percent of the passengers using Greentown airport. Nevertheless, experts reject the claim that turning Hevelia into a full-service airport would end the chronic delays at Greentown. Which of the following, if true, most helps to justify the experts’ position?

Farmer: Worldwide, just three grain crops—rice, wheat, and corn—account for most human caloric intake. To maintain this level of caloric intake and also keep pace with global population growth, yields per acre from each of these crops will have to increase at least 1.5 percent every year, given that the supply of cultivated land is diminishing. Therefore, the government should increase funding for research into new ways to improve yields. Which of the following is an assumption on which the farmer’s argument depends?

The air quality board recently informed Coffee Roast, a small coffee roasting firm, of a complaint regarding the smoke from its roaster. Recently enacted air quality regulations require machines roasting more than 10 pounds of coffee to be equipped with expensive smoke-dissipating afterburners. The firm, however, roasts only 8 pounds of coffee at a time. Nevertheless, the company has decided to purchase and install an afterburner. Which of the following, if true, most strongly supports the firm’s decision?

People who do regular volunteer work tend to live longer, on average, than people who do not. It has been found that “doing good,” a category that certainly includes volunteer work, releases endorphins, the brain’s natural opiates, which induce in people a feeling of well-being. Clearly, there is a connection: regular releases of endorphins must in some way help to extend people’s lives. Which of the following, if true, most seriously undermines the force of the evidence given as support for the hypothesis that endorphins promote longevity?

A study compared a sample of Swedish people older than 75 who needed in-home assistance with a similar sample of Israeli people. The people in the two samples received both informal assistance, provided by family and friends, and formal assistance, professionally provided. Although Sweden and Israel have equally well-funded and comprehensive systems for providing formal assistance, the study found that the people in the Swedish sample received more formal assistance, on average, than those in the Israeli sample. Which of the following, if true, does most to explain the difference that the study found?

Film director: It is true that certain characters and plot twists in my newly released film The Big Heist are similar to characters and plot twists in Thieves, a movie that came out last year. Pointing to these similarities, the film studio that produced Thieves is now accusing me of taking ideas from that film. The accusation is clearly without merit. All production work on The Big Heist was actually completed months before Thieves was released. Which of the following, if true, provides the strongest support for the director’s position?

In Mernia, commercial fossil hunters often sell important fossils they have found, not to universities or museums but to individual collectors, who pay much better but generally do not allow researchers access to their collections. To increase the number of fossils available for research, some legislators propose requiring all fossils that are found in Mernia to be sold only to universities or museums. Which of the following, if true, most strongly indicates that the legislators’ proposal will fail to achieve its goal?

Economist: Tropicorp, which constantly seeks profitable investment opportunities, has been buying and clearing sections of tropical forest for cattle ranching, although pastures newly created there become useless for grazing after just a few years. The company has not gone into rubber tapping, even though greater profits can be made from rubber tapping, which leaves the forest intact. Thus, some environmentalists argue that **Tropicorp’s actions do not serve even its own economic interest.** However, the initial investment required for a successful rubber-tapping operation is larger than that needed for a cattle ranch; there is a shortage of workers employable in rubber-tapping operations; and taxes are higher on profits from rubber tapping than on profits from cattle ranching. Consequently, **the environmentalists’ conclusion is probably wrong.** In the economist’s argument, the two boldfaced portions play which of the following roles?

Brown tides are growths of algae on the sea’s surface that prevent sunlight from reaching marine plants below, thereby destroying not only the plants but also the shellfish that live off these plants. Biologists recently isolated a virus that, when added to seawater, kills the algae that cause brown tides. Adding large quantities of this virus to waters affected by brown tides will therefore make it possible to save the populations of shellfish that inhabit those waters. Which of the following, if true, provides the most support for the conclusion of the argument?

In persons with astigmatism, the clear outer layer of the eye is deformed in a way that impairs and sometimes distorts vision. The elongated figures in the paintings of El Greco (1541–1614) were so unusual that some critics sought to explain them by hypothesizing that, without knowing it, El Greco had an astigmatism that caused everything to appear to him in the distorted way that was characteristic of his painted figures. The proposed explanation is most vulnerable to the criticism that it fails to

Marketing executive for Magu Corporation: Whenever Magu opens a manufacturing facility in a new city, the company should sponsor, or make donations to, a number of nonprofit organizations in that city. Doing so would improve Magu’s image in the community, and thus the money spent on such charitable ventures would lead to increased sales. Which statement would, if true, point to the most serious weakness in the marketing executive’s advice?

In the last few years, plant scientists have been able to genetically engineer seeds to produce crops highly resistant to insect damage. Farmers growing crops with these seeds will be able to spend significantly less on pesticides. This cost reduction would more than make up for the higher cost of the genetically engineered seeds. Clearly, therefore, farmers who grow crops from genetically engineered seeds will be able to reduce their costs by using them. Which of the following, if true, most weakens the argument?

Educational theorist: Recent editorials have called for limits on the amount of homework assigned to schoolchildren younger than 12. They point out that free-time activities play an important role in childhood development and that homework in large quantities can severely restrict children’s free time, hindering their development. But the actual average homework time for children under 12—little more than 30 minutes per night—leaves plenty of free time. In reality, therefore, the editorials’ rationale cannot justify the restriction they advocate. Which of the following, if true, would most seriously call into question the educational theorist’s conclusion?

Thyrian lawmaker: Thyria’s Cheese Importation Board inspects all cheese shipments to Thyria and rejects shipments not meeting specified standards. Yet only 1 percent is ever rejected. Therefore, since the health consequences and associated economic costs of not rejecting that 1 percent are negligible, whereas the board’s operating costs are considerable, for economic reasons alone the board should be disbanded. Consultant: I disagree. The threat of having their shipments rejected deters many cheese exporters from shipping substandard product. The consultant responds to the lawmaker’s argument by

The tulu, a popular ornamental plant, does not reproduce naturally and is only bred and sold by specialized horticultural companies. Unfortunately, the tulu is easily devastated by a contagious fungal rot. The government ministry plans to reassure worried gardeners by requiring all tulu plants to be tested for fungal rot before being sold. However, infected plants less than 30 weeks old have generally not built up enough fungal rot in their systems to be detected reliably. And many tulu plants are sold before they are 24 weeks old. Which of the following, if performed by the government ministry, could logically be expected to overcome the problem with their plan to test for the fungal rot?

While many people think of genetic manipulation of food crops as being aimed at developing larger and larger plant varieties, some plant breeders have in fact concentrated on discovering or producing dwarf varieties, which are roughly half as tall as normal varieties. Which of the following would, if true, most help to explain the strategy of the plant breeders referred to above?

Secret passwords are often used to control access to computers. When employees select their own passwords, they frequently choose such easily guessed passwords as their initials or birth dates. To improve security, employers should assign randomly generated passwords to employees rather than allowing employees to make up their own. Which of the following, if true, most seriously undermines the conclusion drawn above?

The economy around Lake Paqua depends on fishing of the lake’s landlocked salmon population. In recent years, scarcity of food for salmon there has caused a decline in both the number and the size of the adult salmon in the lake. As a result, the region’s revenues from salmon fishing have declined significantly. To remedy this situation, officials plan to introduce shrimp, which can serve as a food source for adult salmon, into Lake Paqua. Which of the following, if true, most seriously calls into question the plan’s chances for success?

Airline representative: The percentage of flight delays caused by airline error decreased significantly this year. This indicates that airlines listened to complaints about preventable errors and addressed the problems. Although delays caused by weather and other uncontrollable factors will always be part of travel, preventable delays are clearly decreasing. Which of the following most clearly points to a logical flaw in the representative’s reasoning?

Although the school would receive financial benefits if it had soft drink vending machines in the cafeteria, we should not allow them. Allowing soft drink machines there would not be in our students’ interest. If our students start drinking more soft drinks, they will be less healthy. The argument depends on which of the following?