11. In 1990 major engine repairs were performed on 10 percent of the cars that had been built by the National Motor Company in the 1970s and that were still registered. However, the corresponding figure for the cars that the National Motor Company had manufactured in the 1960s was only five percent.

Which of the following, if true, most helps to explain the discrepancy？

（A） Government motor vehicle regulations generally require all cars, whether old or new, to be inspected for emission levels prior to registration.

（B） Owners of new cars tend to drive their cars more carefully than do owners of old cars.

（C） The older a car is, the more likely it is to be discarded for scrap rather than repaired when major engine work is needed to keep the car in operation.

（D） The cars that the National Motor Company built in the 1970s incorporated simplified engine designs that made the engines less complicated than those of earlier models.

（E） Many of the repairs that were performed on the cars that the National Motor Company built in the 1960s could have been avoided if periodic routine maintenance had been performed.

12. No mathematician today would flatly refuse to accept the results of an enormous computation as an adequate demonstration of the truth of a theorem. In 1976, however, this was not the case. Some mathematicians at that time refused to accept the results of a complex computer demonstration of a very simple mapping theorem. Although some mathematicians still hold a strong belief that a simple theorem ought to have a short, simple proof, in fact, some simple theorems have required enormous proofs.

If all of the statements in the passage are true, which one of the following must also be true？

（A） Today, some mathematicians who believe that a simple theorem ought to have a simple proof would consider accepting the results of an enormous computation as a demonstration of the truth of a theorem.

（B） Some individuals who believe that a simple theorem ought to have a simple proof are not mathematicians.

（C） Today, some individuals who refuse to accept the results of an enormous computation as a demonstration of the truth of a theorem believe that a simple theorem ought to have a simple proof.

（D） Some individuals who do not believe that a simple theorem ought to have a simple proof would not be willing to accept the results of an enormous computation as proof of a complex theorem.

（E） Some nonmathematicians do not believe that a simple theorem ought to have a simple proof.

13. If you climb mountains, you will not live to a ripe old age. But you will be bored unless you climb mountains. Therefore, if you live to a ripe old age you will have been bored.

Which of the following most closely parallels the reasoning in the arguments above？

（A） If you do not try to swim, you will not learn how to swim. But you will not be safe in boats if you do not learn how to swim. Therefore, you must try to swim.

（B） If you do not play golf, you will not enjoy the weekend. But you will be tired next week unless you relax during the weekend. Therefore, to enjoy the weekend, you will have to relax by playing golf.

（C） If you work for your candidate, you will not improve your guitar playing. But you will neglect your civic duty unless you work for your candidate. Therefore, if you improve your guitar playing, you will have neglected your civic duty.

（D） If you do not train, you will not be a good athlete. But you will become exhausted easily unless you train. Therefore, if you train, you will not have become exhausted easily.

（E） If you spend all of your money, you will not become wealthy. But you will become hungry unless you spend all of your money. Therefore, if you become wealthy, you will not become hungry.

14. Marine biologists had hypothesized that lobsters kept together in lobster traps eat one another in response to hunger. Periodic checking of lobster traps, however, has revealed instances of lobsters sharing traps together for weeks. Eight lobsters even shared one trap together for two months without eating one another. The marine biologists' hypothesis, therefore, is clearly wrong.

The argument against the marine biologists' hypothesis is based on which one of the following assumptions？

（A） Lobsters not caught in lobster traps have been observed eating one another.

（B） Two months is the longest known period during which eight or more lobsters have been trapped together.

（C） It is unusual to find as many as eight lobsters caught together in one single trap.

（D） Members of other marine species sometimes eat their own kind when no other food sources are available.

（E） Any food that the eight lobsters in the trap might have obtained was not enough to ward off hunger.

15. Eight years ago hunting was banned in Greenfield County on the grounds that hunting endangers public safety. Now the deer population in the county is six times what it was before the ban. Deer are invading residential areas. Damaging property and causing motor vehicle accidents that result in serious injury to motorists. Since there were never any hunting=related injuries in the county, clearly the ban was not only unnecessary but has created a danger to public safety that would not otherwise exist.

Which one of the following, if true, provides the strongest additional support for the conclusion above？

（A） In surrounding counties, where hunting is permitted, the size of the deer population has not increased in the last eight years.

（B） Motor vehicle accidents involving deer often result in damage to the vehicle, injury to the motorist, or both.

（C） When deer populations increase beyond optimal size, disease and malnutrition become more widespread among the deer herds.

（D） In residential areas in the county, many residents provide food and salt for deer.

（E） Deer can cause extensive damage to ornamental shrubs and trees by chewing on twigs and saplings