It was never clear _______ the man hadn’t reported the accident sooner.
问题描述：
It was never clear _______ the man hadn’t reported the accident sooner.
A.that B.how C.when D.why
为什么不选D?
答
这是一个it引导的主语从句,it是形式主语,真正的主语是后面that引导的从句,why是引导原因状语从句,所以这不能选D.加油!