虚拟语气could/should/would/might +have done 用法的差别？麻烦解答一下我的问题，谢谢！

Question

1.It's a great pity that you _____ have done such a thing.
A. ought to B.should C.could D.might

2.As I have nothing to do now,I _____ as well go with you.
A.should B.would C.could D.might

3. _______ he could late ,give him the message.
A.Should B.Would C. Had D .Did

Answer 1

could have done本来能够做什么，事实上没做
should have done本来应该做
would have done将来可能做
might have done可能做了
1. 很可惜你没做那件事，事实上你能够做的，所以选C
2. might as well 做什么更好，既然我无事可做，还不如跟着你好了
3. B， 对将来时的虚拟，他可能会迟到，告诉他这个消息

Answer 2

could have done本来可以做而没有做
should have done本来应该做而没有做
would have done 表示将来,是过去看现在是将来,此时说的时候是过去
might have done 表示一种很弱的可能性
这三道题 :C,B,C

Answer 3

1. The answer is (C.could)
（1）ought to/should have done sth, 表示过去应该做某事，但却没做，带有一种责怪的语气。
例如： You shouldn't have let her come to my office.
译为，你不应该让你给她进我的办公室。（实际上让她进了，表示责备）
（2）could have done sth, 表示过去能做某事，但却没做。
由于此句前面用了”It's a great pity “， 这就暗指了它不想表达责怪的想法， 故不用should而用could。
（3）might have done sth 表示可能作过某事。它是对过去动作，是否发生过，进行推测。故不适用。
2. might as well 做什么更好，既然我无事可做，还不如跟着你好了