新东方补充教材蓝皮书39题

逻辑讲义第39题中

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.

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.

正确答案是A ,可我当时选了D, 有哪位能帮忙解释一下A正确的分析思路吗，我现在脑子发滞，想不明白了。