Lofgren's disease has been observed frequently in commercially raised cattle but very rarely in chickens. Both cattle and chickens raised for meat are often fed the type of feed that transmits the virus that causes the disease. Animals infected with the virus take more than a year to develop symptoms of Lofgren's disease, however, and chickens commercially raised for meat, unlike cattle, are generally brought to market during their first year of life.

Which of the following is most strongly supported by the information provided?

Plankton generally thrive in areas of the ocean with sufficient concentrations of certain nitrogen compounds near the surface, where plankton live. Nevertheless, some areas, though rich in these nitrogen compounds, have few plankton. These areas have particularly low concentrations of iron, and oceanographers hypothesize that this shortage of iron prevents plankton from thriving. However, an experimental release of iron compounds into one such area failed to produce a thriving plankton population, even though local iron concentrations increased immediately.

Which of the following, if true, argues most strongly against concluding, on the basis of the information above, that the oceanographers' hypothesis is false?

In 1960's studies of rats, scientists found that crowding increases the number of attacks among the animals significantly. But in recent experiments in which rhesus monkeys were placed in crowded conditions, although there was an increase in instances of "coping" behavior-such as submissive gestures and avoidance of dominant individuals-attacks did not become any more frequent. Therefore it is not likely that, for any species of monkey, crowding increases aggression as significantly as was seen in rats.

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

Whales originated in the freshwater lakes and rivers of ancient Asia about sixty million years ago. Not until about ten million years later did species of whales develop specialized kidneys enabling them to drink salt water. Although fossil evidence shows that some early whale species that lacked such kidneys sometimes swam in the Earth's saltwater oceans, these species must have had to return frequently to freshwater rivers to drink.

Which of the following is most strongly supported by the information given?

Critics of certain pollution-control regulations have claimed that the money spent over the last decade in order to reduce emissions of carbon monoxide and of volatile organic compounds has been wasted. The evidence they offer in support of this claim might appear compelling: despite the money spent, annual emissions of these pollutants have been increasing steadily. This evidence is far from adequate, however, since over the last decade a substantial number of new industrial facilities that emit these pollutants have been built.

In the reasoning given, the two portions in boldface play which of the following roles?

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?

Educational Theorist: Recent editorials have called for limits on the amount of homework assigned to children. They point out that free-time activities play an important role in childhood development and that large amounts of homework reduce children's free time, hindering their development. But the average homework time for a ten year old, for example, is little more than 30 minutes per night. Clearly, therefore, there is no need to impose the limits these editorials are calling for.

Which of the following is an assumption on which the educational theorist's argument relies?

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?

A medieval manuscript called L contains all eighteen extant tragedies by the Greek playwright Euripides. Of these, ten called the "select plays," are accompanied in L by ancient commentaries and also appear in other medieval manuscripts; this group includes some of Euripides' best-known works, including the Medea. The other eight, which appear only in L, are called the "alphabeticals" because they appear in alphabetical order, without commentary. The Electra is one of the "alphabeticals".

Which of the following can be reliably concluded on the basis of the Statements given?

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?