Safety consultant: Judged by the number of injuries per licensed vehicle, minivans are the safest vehicles on the road. However, in carefully designed crash tests, minivans show no greater ability to protect their occupants than other vehicles of similar size do. Thus, the reason minivans have such a good safety record is probably not that they are inherently safer than other vehicles, but rather that they are driven primarily by low-risk drivers.

Which one of the following, if true, most strengthens the safety consultant’s argument?

Consumer advocate: There is no doubt that the government is responsible for the increased cost of gasoline, because the government’s policies have significantly increased consumer demand for fuel, and as a result of increasing demand, the price of gasoline has risen steadily.

Which one of the following is an assumption required by the consumer advocate’s argument?

Public health experts have waged a long-standing educational campaign to get people to eat more vegetables, which are known to help prevent cancer. Unfortunately, the campaign has had little impact on people’s diets. The reason is probably that many people simply dislike the taste of most vegetables. Thus, the campaign would probably be more effective if it included information on ways to make vegetables more appetizing.

Which one of the following, if true, most strengthens the argument?

Pure science—research with no immediate commercial or technological application—is a public good. Such research requires a great amount of financial support and does not yield profits in the short term. Since private corporations will not undertake to support activities that do not yield short-term profits, a society that wants to reap the benefits of pure science ought to use public funds to support such research.

The claim about private corporations serves which one of the following functions in the argument?

Doctor: Being overweight has long been linked with a variety of health problems, such as high blood pressure and heart disease. But recent research conclusively shows that people who are slightly overweight are healthier than those who are considerably underweight. Therefore, to be healthy, it suffices to be slightly overweight.

The argument’s reasoning is flawed because the argument

Some doctors believe that a certain drug reduces the duration of episodes of vertigo, claiming that the average duration of vertigo for people who suffer from it has decreased since the drug was introduced. However, during a recent three-month shortage of the drug, there was no significant change in the average duration of vertigo. Thus, we can conclude that the drug has no effect on the duration of vertigo.

Which one of the following is an assumption required by the argument?

Many important types of medicine have been developed from substances discovered in plants that grow only in tropical rain forests. There are thousands of plant species in these rain forests that have not yet been studied by scientists, and it is very likely that many such plants also contain substances of medicinal value. Thus, if the tropical rain forests are not preserved, important types of medicine will never be developed.

Which one of the following is an assumption required by the argument?

Earthworms, vital to the health of soil, prefer soil that is approximately neutral on the acid-to-alkaline scale. Since decomposition of dead plants makes the top layer of soil highly acidic, application of crushed limestone, which is highly alkaline, to the soil’s surface should make the soil more attractive to earthworms.

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

Early urban societies could not have been maintained without large-scale farming nearby. This is because other methods of food acquisition, such as foraging, cannot support populations as dense as urban ones. Large-scale farming requires irrigation, which remained unfeasible in areas far from rivers or lakes until more recent times.

Which one of the following is most strongly supported by the information above?

Robust crops not only withstand insect attacks more successfully than other crops, they are also less likely to be attacked in the first place, since insects tend to feed on weaker plants. Killing insects with pesticides does not address the underlying problem of inherent vulnerability to damage caused by insect attacks. Thus, a better way to reduce the vulnerability of agricultural crops to insect pest damage is to grow those crops in good soil—soil with adequate nutrients, organic matter, and microbial activity.

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

People perceive color by means of certain photo-pigments in the retina that are sensitive to certain wavelengths of light. People who are color-blind are unable to distinguish between red and green, for example, due to an absence of certain photo-pigments. What is difficult to explain, however, is that in a study of people who easily distinguish red from green, 10 to 20 percent failed to report distinctions between many shades of red that the majority of the subjects were able to distinguish.

Each of the following, if true, helps to explain the result of the study cited above EXCEPT:

Because of increases in the price of oil and because of government policies promoting energy conservation, the use of oil to heat homes fell by 40 percent from 1970 to the present, and many homeowners switched to natural gas for heating. Because switching to natural gas involved investing in equipment, a significant switch back to oil in the near future is unlikely.

The prediction that ends the passage would be most seriously called into question if it were true that in the last few years