Astronomer: Observations of the Shoemaker-Levi comet on its collision course with Jupiter showed that the comet broke into fragments before entering Jupiter's atmosphere in 1994, but they did not show how big those fragments were. Nevertheless, some indication of their size can be inferred from spectrographic analyses of Jupiter's outer atmosphere. After the fragments' entry, these analyses revealed unprecedented traces of sulfur. The fragments themselves almost certainly contained no sulfur, but astronomers believe that the cloud layer below Jupiter's outer atmosphere does contain sulfur. Since sulfur would have seeped into the outer atmosphere if comet fragments had penetrated this cloud layer, it is likely that some of the fragments were at least large enough to have passed through Jupiter's outer atmosphere without being burned up.

In the astronomer's argument, the two portions in boldface play which of the following roles?

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?

Background information: This year, each film submitted to the Barbizon Film Festival was submitted in one of ten categories. For each category, there was a panel that decided which submitted films to accept.Fact 1: Within each category, the rate of acceptance for domestic films was the same as that for foreign films. Fact 2: The overall rate of acceptance of domestic films was significantly higher than that of foreign films.

In light of the background information, which of the following, if true, can account for fact 1 and fact 2 both being true of the submissions to this year's Barbizon Film Festival?

Industrial accidents are more common when some of the people in safety-sensitive jobs have drinking problems than when none do. Since, even after treatment, people who have had drinking problems are somewhat more likely than other people to have drinking problems in the future, any employer trying to reduce the risk of accidents should bar anyone who has ever been treated for a drinking problem from holding a safety-sensitive job.

Which of the following, if true, most seriously undermines the argument above?

A major chemical spill occurred five years ago at Baker's Beach, the world's sole nesting ground for Merrick sea turtles, and prevented nearly all the eggs laid that year from hatching. Yet the number of adult female Merricks returning to lay their eggs at Baker's Beach has actually increased somewhat since five years ago. Clearly, environmentalists' prediction that the world's Merrick population would decline as a result of the spill has proven unfounded.

Which of the following, if true, most seriously undermines the argument offered in refutation of the environmentalists' prediction?

In recent years, networks of fiber-optic cable have been replacing electrical wire for transmitting telecommunications signals. Signals running through fiber-optic cables deteriorate, and so the signals must be run through a piece of equipment called a regenerator before being transmitted farther. Light-Line is the leading manufacturer of signal regenerators. Therefore, Light-Line is one of the companies that will most benefit if new long-distance fiber-optic telecommunications networks are constructed.

Which of the following, if true, casts the most doubt on the prediction about Light-Line's prospects?

Last August the XT chain of gasoline stations had a temporary sales promotion in effect. In the promotion , any customer who made a purchase of ten or more gallons of gasoline was entitled to a free car wash . For the month of August , XT experienced a ten percent increase in gasoline sales as compared to sales in August the previous year so evidently the promotion was successful as a means of boosting sales.

In evaluating the argument , it would be most helpful to answer which of the following ?

The sense of delayed gratification, of working now for later pleasure, has helped shape the economic behavior of our society. However, that sense is no longer nurtured as consistently in our children as it once was. For example, it used to take a bit of patience to put together the toys that children got in cereal boxes; now the toys come from the boxes whole.

Which of the following is an assumption of the passage above?

Fearing competition from stores that rent video games for home use, owners of stores that sell video games lobbied for protective legislation. Citing as a precedent legislation that postpones home film rentals until one year after general release to theaters, the video sellers proposed as an equitable solution a plan that would postpone rental of any video game until it had been available for sale for one year.

Which of the following, if true, would support an objection by owners of video rental stores that the fairness of the proposed legislation is not supported by the precedent cited?

Because ethylene dibromide, a chemical used to fumigate grain, was blamed for the high rate of nerve damage suffered by people who work in grain-processing plants, many such plants switched to other chemical fumigants two years ago. Since then, however, the percentage of workers at these plants who were newly diagnosed with nerve damage has not dropped significantly. Therefore, either ethylene dibromide was wrongly blamed or else the new chemicals also cause nerve damage.

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

In the past the country of Siduria has relied heavily on imported oil. Siduria recently implemented a program to convert heating systems from oil to natural gas. Siduria already produces more natural gas each year than it burns, and oil production in Sidurian oil fields is increasing at a steady pace. If these trends in fuel production and usage continue, therefore, Sidurian reliance on foreign sources for fuel should decline soon.

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

Many large department stores in Montalia now provide shopping carts for their customers. Since customers using shopping carts tend to buy more than those without shopping carts, most of these stores are experiencing strong sales growth, while most other department stores are not. Therefore, in order to boost sales, managers of Jerrod's, Montalia's premier department store, are planning to purchase shopping carts and make them available to the store's customers next month.

Which of the following, if true, casts most doubt whether the managers' plan, if implemented, will achieve its goal?

A mosquito bite can transmit to a person the parasite that causes malaria, and the use of mosquito nets over children's beds can significantly reduce the incidence of malarial infection for children in areas where malaria is common. Yet public health officials are reluctant to recommend the use of mosquito nets over children's beds in such areas.

Which of the following, if true, would provide the strongest grounds for the public health officials' reluctance?

For similar cars and drivers, automobile insurance for collision damage has always cost more in Greatport than in Fairmont. Police studies, however, show that cars owned by Greatport residents are, on average, slightly less likely to be involved in a collision than cars in Fairmont. Clearly, therefore, insurance companies are making a greater profit on collision-damage insurance in Greatport than in Fairmont.

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

Criminologist: Some legislators advocate mandating a sentence of life in prison for anyone who, having twice served sentences for serious crimes, is subsequently convicted of a third serious crime. These legislators argue that such a policy would reduce crime dramatically, since it would take people with a proven tendency to commit crimes off the streets permanently. What this reasoning overlooks, however, is that people old enough to have served two prison sentences for serious crimes rarely commit more than one subsequent crime. Filling our prisons with such individuals would have exactly the opposite of the desired effect, since it would limit our ability to incarcerate younger criminals, who commit a far greater proportion of serious crimes.

In the argument as a whole, the two boldfaced portions play which of the following roles?