请教一道逻辑题

zm_patrick

A recent survey of all auto accident victims in Dole County found that eighty percent of the severely injured drivers and front-seat passengers 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 risks of being 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 twenty percent were waering seat belts at the tme of their accidents.

B)Considerably more than 20 percent of drivers and fromt-seat passengers in Dole County always wear seat belts when travelling by car

C)More drivers and fromt-seat passengers in the survey than rear-seat passengers were very severely injured.

D)More than half of the drivers and fromt-seat passengers in the survey were not wearing seat belts at the time of their accidents

E)Most of the auto accidents reported to the police in Dole County do not involve any serious injury.

Why is answer is B? Even if I was enlightened by the answer guide on thinking of this question from the Mathematics Set, I couldn't understand the answer at all yet. Please teach me.h

sophiaruan

逻辑链：80%司机和前座的人出车祸时没有系安全带====》坐在前排系安全带减少很大的危险

问：下面那个为正确时上面的结论才能成立

A:司机和前排乘客中，多于20%的人出车祸时系安全带。系安全带也不安全，这应该是削弱的。

B：超过20%的司机和前排乘客总是乘车的时候系安全带。因为总是系安全带，总是安全的，所以减少危险了。

C：司机和前排乘客比后排乘客伤的更严重。前排和后排比较，无关。

D：超过50%的司机和前排乘客在车祸时没有系安全带。文中说80%，重复论据无意义。

E：被报道的车祸都不严重。无关选项。

如有不对请指出，谢谢。

zm_patrick

谢谢你的答复

你列的逻辑链：80%司机和前座的人出车祸时没有系安全带====》坐在前排系安全带减少很大的危险”，

两个疑问：

1 原文好象是说80%的严重受伤的司机和前座的人出车祸时没有系安全带====》坐在前排系安全带减少很大的危险

2 B的意思是远远超过20%的司机和前座的人总是系着安全带，那么为什么又会有80%的司机和前座的人严重受伤呢？如果80%的集合体是指重受伤的司机和前座的人，那么远远超过20%的司机和前座的人总是系着安全带和80%的严重受伤的司机和前座的人出车祸时没有系安全带也没有直接联系啊？如果B改成没有严重受伤的人里面超过80%的系了安全带还差不多。

请指教！

hongrucai

这么解释：如果所有人都没有系安全带，而只有那一部分人出车祸，那么就不能说明安全带能减少危险。所以必须有一个假设就是，大部分人都系了安全带，只有出车祸的那一部份人没有系。这样只有B毕竟比较这个意思