ＧＭＡＴ問題教えて下さい。

On the basisi of the accumulated data from several studies which indicated that when alcohol is consumed before driving the incidence of automobile accidents increases significantly, the federal government has passed strict laws prohibiting drivers from operating their vehicles after consuming specific amounts of alcohol. Surprisingly, it has since been discovered that alarge number of drivers who have not been comsuming alcohol in amounts that exceed legal specifications are still becoming involved in the type of automobile accidents that the laws were designed to reduce , and in the prevention of which they had actually proven to be effective.

Which one of the following , if true, could by itself adepuately explain the unexpected finding reported in the passage?

(A) Many people are defying the law by drinking only slightly less than the legal limit of alcoholic beverages.

(D) The laws prohibiting drinking alcohol and then driving were not designed to prevent all types of accidents, so it is not surprising that some accidents still occur.

アルクの本の問題なのですが、答えが(A)になっております。正直腑に落ちないのですが、どなたか教えて頂けないでしょうか？私は(D)のような気がしてなりません。

ちなみに私はＧＭＡＴをはじめたばかりで、Ｇの正解のルールが良くわかっていないのかもしれませんが・・・。