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

射血分数是指

A．每搏输出量/心室舒张末期容积
B．心排出量/体表面积
C．心室收缩末期容积/心室舒张末期容积
D．心排出量/心室舒张末期容积