No one can recall any detail about the accident.It is at least twenty years since it____

C took place
since前市一般现在时，那么后面的事情就是一般过去时，因为站在现在的角度，since后面的事情是发生在过去的。

A
since后要加过去时
A从时态来讲是最合适的

不 是 hand taken place 而是 “had taken place.” Had taken place 是指过去已经完成的动作和事情

答案 是 A

had took place

a