He should have known the police wouldn't allow it _______.
问题描述:
He should have known the police wouldn't allow it _______.
为什么空格上是填but he didn't 而不是but he couldn't.
答
He should have known the police wouldn't allow it _______.should have known 虚拟语气:本应该知道他本应该知道这是警察不许可的,但他(不知道)如果是but he couldn't,但他不会(不能)知道,不符语意.should是虚...