It only took a short period for the cause of the accident_______.

问题描述:

It only took a short period for the cause of the accident_______.
A.to be found B.to find
C.finding D.being found

A 只用了短短的时间事故原因就被发现.这是翻译,find的被动形式是found,被发现是被动的,所以BCD都不对