Both his parents look sad. Maybe they ________ what happened to him.

A. will know B. knew

C. have known D. had known

 

C

【解析】

试题分析：句意：他的父母看起来很伤心。也许他们知道他发生了什么事。根据语境可知该用现在完成时，所以选C。

考点：考查动词时态。

 

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