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.
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
but he didnt: 但他不知道 ---- he didn't know
but he couldn't: 但他不可能 ----- he couldn't know(错误的, 说不通)
答
He should have known the police wouldn't allow it be he didn't.
他应该知道警察会不允许, 但他不(知道).
couldn't 在这里的意思是不会
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...