would/could/must have done在虚拟语气中怎么用?

题目

would/could/must have done在虚拟语气中怎么用?

答案

would have done本来想要做某事（却没做）could have done 本来能够做某事（却没做）must have done 过去一定做了某事（对过去发生事情肯定的推测）,这三个情态动词加have done,都是对过去发生事情的虚拟,从时态的角度讲是一种过去时.