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 belt, 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.(答案)
B) considerably more than 20 percent of drivers and front-seat passengers in Dole Country 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 injuried.
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 Country do not involve any serious injury.作者: Steven0124 时间: 2012-8-28 20:59
Necessary assumption. Use negation.作者: xiaohaotoutou 时间: 2012-8-29 06:23
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.作者: xiaohaotoutou 时间: 2012-8-30 20:28
其实我就是没明白那of the severely injured drivers and front-seat passengers,80percent were not wearing seat
