大全 2-14 请指点下

happy8young

A recent survey of all autoaccident victims in Dole County found that, of the severely injured drivers andfront-seat passengers, 80 percent were not wearing seat belts at the time oftheir accidents. This indicates that, by wearing seat belts, drivers andfront-seat passengers can greatly reduce their risk of being severely injuredif they are in an auto accident.
Theconclusion above is not properly drawn unless which of the following is true?
(A) Of all the drivers and front-seatpassengers in the survey, more than 20 percent were wearing seat belts at thetime of their accidents.
(B) Considerably more than 20 percent ofdrivers and front-seat passengers in Dole County always wear seat belts whentraveling by car.
(C) More drivers and front-seatpassengers in the survey than rear-seat passengers were very severely injured.
(D) More than half of the drivers andfront-seat passengers in the survey were not wearing seat belts at the time oftheir accidents.（A）
(E) Most of the auto accidents reportedto police in Dole County do not involve any serious injury.


没什么思路，请指点下。这类题怎么做，万分感谢。

willgoeu

大体结构：
已知：在车祸受伤的这些人中，80%的重伤人员没系安全带
结论：系安全带可降低重伤风险
问：怎样加强
A说20%多的重伤的人系了安全带，把这再结和题干信息可知没系安全带的人受重伤的概率是系了的4倍因此便可推出结论：系安全带可降低重伤风险
BCDE我都用无关来排除掉了：本文是研究重伤与系安全带的关系，剩下四个都扯到别的事情上了。。。
PS：如果我的思路正确的话，我认为这题出的不好：因为题目说80%的重伤人员没系安全带同时也就暗含着20%的人系了，（因为就这两种情况啊）干吗还要拿出来当一个加强的条件呢？？
欢迎讨论！！！

honeybee316

说一下我的思路。
题干：在所有的重伤调查人中，80%没有系安全带   （注意限定词是severely injured ）
结论：系安全带会降低重伤的风险（注意限定词还是severely injured ）
A 选项：在所有的车祸调查人中，多于20%系了安全带   （没有限定词 ！意思就是包括重伤以及不重伤的车祸）
那么就可以直接推，在车祸中受伤的人（包括重伤轻伤）是少于80%的人没有系安全带（随便定个75%撒~~~）
这样，和原文中的在车祸中受重伤的人有80%没有系安全带就可以进行比较，得出的结论就是系安全带可以降低在车祸中受重伤的风险！！（也可以直接定个具体的数值去看）
此题我觉得关键就是分清重伤和车祸受伤两个概念，降低重伤的概率不等于降低车祸的概率。
不知道说清楚了么。。。

happy8young

thanks !