Critical Reasoning

A drug that is highly effective in treating many types of infection can, at present, be obtained only from the bark of the ibora, a tree that is quite rare in the wild. It takes the bark of 5,000 trees to make one kilogram of the drug. It follows, therefore, that continued production of the drug must inevitably lead to the ibora's extinction. B The drug made from ibora bark is expensive to produce. C The leaves of the ibora are used in a number of medical products. D The ibora can be propagated from cuttings and grown under cultivation. E The ibora generally grows in largely inaccessible places.

In Washington County, attendance at the movies is just large enough for the cinema operators to make modest profits. The size of the county's population is stable and is not expected to increase much. Yet there are investors ready to double the number of movie screens in the county within five years, and they are predicting solid profits both for themselves and for the established cinema operators. Which of the following, if true about Washington County, most helps to provide a justification for the investors' prediction?

Kale has more nutritional value than spinach. But since collard greens have more nutritional value than lettuce, it follows that kale has more nutritional value than lettuce. Any of the following, if introduced into the argument as an additional premise, makes the argument above logically correct EXCEPT:

In comparison to the standard typewriter keyboard, the EFCO keyboard, which places the most-used keys nearest the typist�s strongest fingers, allows faster typing and results in less fatigue. Therefore, replacement of standard keyboards with the EFCO keyboard will result in an immediate reduction of typing costs. Which of the following, if true, would most weaken the conclusion drawn above?

When hypnotized subjects are told that they are deaf and are then asked whether they can hear the hypnotist, they reply, "No." Some theorists try to explain this result by arguing that the selves of hypnotized subjects are dissociated into separate parts, and that the part that is deaf is dissociated from the part that replies. Which of the following challenges indicates the most serious weakness in the attempted explanation described above?

In Swartkans territory, archaeologists discovered charred bone fragments dating back 1 million years. Analysis of the fragments, which came from a variety of animals, showed that they had been heated to temperatures no higher than those produced in experimental campfires made from branches of white stinkwood, the most common tree around Swartkans. Which of the following, if true, would, together with the information above, provide the best basis for the claim that the charred bone fragments are evidence of the use of fire by early hominids?

The technological conservatism of bicycle manufacturers is a reflection of the kinds of demand they are trying to meet. The only cyclists seriously interested in innovation and willing to pay for it are bicycle racers. Therefore, innovation in bicycle technology is limited by what authorities will accept as standard for purposes of competition in bicycle races. Which of following is an assumption made in drawing the conclusion above?

Roland: The alarming fact is that 90 percent of the people in this country now report that they know someone who is unemployed. Sharon: But a normal, moderate level of unemployment is 5 percent, with 1 out of 20 workers unemployed. So at any given time if a person knows approximately 50 workers, 1 or more will very likely be unemployed. Sharon's argument relies on the assumption that

Many breakfast cereals are fortified with vitamin supplements. Some of these cereals provide 100 percent of the recommended daily requirement of vitamins. Nevertheless, a well-balanced breakfast, including a variety of foods, is a better source of those vitamins than are such fortified breakfast cereals alone. Which of the following, if true, would most strongly support the position above?

"Life expectancy" is the average age at death of the entire live-born population. In the middle of the nineteenth century, life expectancy in North America was 40 years, whereas now it is nearly 80 years. Thus, in those days, people must have been considered old at age that we now consider the prime of life. Which of the following, if true, undermines the argument above?

The Plexis Corporation, a leading computer chip manufacturer, is currently developing a new chip, which is faster and more efficient than any computer chip currently in use. The new chip will be released for sale in twelve months. Plexis� market research has shown that initial sales of the new chip would be maximized by starting to advertise it now, but the company has decided to wait another six months before doing so. Which of the following, if true, provides the Plexis Corporation with the best reason for postponing advertising its new chip?

Offshore oil-drilling operations entail an unavoidable risk of an oil spill, but importing oil on tankers presently entails an even greater such risk per barrel of oil. Therefore, if we are to reduce the risk of an oil spill without curtailing our use of oil, we must invest more in offshore operations and import less oil on tankers. Which of the following, if true, most seriously weakens the argument above.

Caterpillars of all species produce an identical hormone called "juvenile hormone" that maintains feeding behavior. Only when a caterpillar has grown to the right size for pupation to take place does a special enzyme halt the production of juvenile hormone. This enzyme can be synthesized and will, on being ingested by immature caterpillars, kill them by stopping them from feeding. Which of the following, if true, most strongly supports the view that it would not be advisable to try to eradicate agricultural pests that go through a caterpillar stage by spraying croplands with the enzyme mentioned above?

Cable-television spokesperson: Subscriptions to cable television are a bargain in comparison to �free� television. Remember that �free� television is not really free. It is consumers, in the end, who pay for the costly advertising that supports �free� television. Which of the following, if true, is most damaging to the position of the cable-television spokesperson?

Robot satellites relay important communications and identify weather patterns. Because the satellites can be repaired only in orbit, astronauts are needed to repair them. Without repairs, the satellites would eventually malfunction. Therefore, space flights carrying astronauts must continue. Which of the following, if true, would most seriously weaken the argument above?

Advertisement: Today's customers expect high quality. Every advance in the quality of manufactured products raises customer expectations. The company that is satisified with the current quality of its products will soon find that its customers are not. At MegaCorp, meeting or exceeding customer expectations is our goal! Which of the following must be true on the basis of the statements in the advertisement above?

A report that many apples contain a cancer-causing preservative called Alar apparently had little effect on consumers. Few consumers planned to change their apple-buying habits as a result of the report. Nonetheless, sales of apples in grocery stores fell sharply in March, a month after the report was issued. B Because of a growing number of food-safety warnings, consumers in March were indifferent to such warnings. C The report was delivered on television and also appeared in newspapers. D The report did not mention that any other fruit contains Alar, although the preservative is used on other fruit. E Public health officials did not believe that apples posed a health threat because only minute traces of Alar were present in affected apples.

Products sold under a brand name used to command premium prices because, in general, they were superior to nonbrand rival products. Technical expertise in product development has become so widespread, however, that special quality advantages are very hard to obtain these days and even harder to maintain. As a consequence, brand-name products generally neither offer higher quality nor sell at higher prices. Paradoxically, brand names are a bigger marketing advantage than ever. Which of the following, if true, most helps to resolve the paradox outlined above?

Although aspirin has been proven to eliminate moderate fever associated with some illnesses, many doctors no longer routinely recommend its use for this purpose. A moderate fever stimulates the activity of the body�s disease-fighting white blood cells and also inhibits the growth of many strains of disease-causing bacteria. If the statements above are true, which of the following conclusions is most strongly supported by them ?

Firms adopting �profit-related-pay� (PRP) contracts pay wages at levels that vary with the firm�s profits. In the metalworking industry last year, firms with PRP contracts in place showed productivity per worker on average 13 percent higher than that of their competitors who used more traditional contracts. If, on the basis of the evidence above, it is argued that PRP contracts increase worker productivity, which of the following, if true, would most seriously weaken that argument?