30.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 sear 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 sear belts at the time of their accidents.