请教新东方蓝皮书上的题

lemonsmell · 发表于 2011-1-24 13:08:06

A recent survey of all auto accident victims in Dole County found that, of the severely injured drivers and front-seat passengers, 80 percent were not wearing seat belts at the time of their accidents. This indicates that, by wearing seat belts, drivers and front-seat passengers can greatly reduce their risk of being severely injured if they are in an auto accident.

The conclusion above is not properly drawn unless which of the following is true?

(A) Of all the drivers and front-seat passengers in the survey, more than 20 percent were wearing seat belts at the time of their accidents.
(B) Considerably more than 20 percent of drivers and front-seat passengers in Dole County always wear seat belts when traveling by car.
(C) More drivers and front-seat passengers in the survey than rear-seat passengers were very severely injured.
(D) More than half of the drivers and front-seat passengers in the survey were not wearing seat belts at the time of their accidents.
(E) Most of the auto accidents reported to police in Dole County do not involve any serious injury.

答案是a,但感觉这个答案并没有从逻辑上作证明，只是再重复题干，希望大家给点提示。

sdcar2010 · 发表于 2011-1-24 20:36:36

No. You need to pay attention to details. "all auto accident victims" vs. "severely injured drivers and front-seat passengers." The premise is that "80% of the severely injured drivers and front-seat passengers" were not wearing set belts. The conclusion is that "by wearing seat belts, drivers and front-seat passengers can greatly reduce their risk of being severely injured if they are in an auto accident."

What about those who were not injuried in an accident? How many of them wearing seat belts? If none of them wore seat belts, then the conclusion is wrong.

A is a necessary assumption.

lemonsmell · 发表于 2011-1-25 12:27:52

Got it. Thx!

请教新东方蓝皮书上的题

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