2)may(might)have+过去分词

A.表示对过去情况的推测，意为，“可能已做某事”。

He may have heard the news.

I might have come to a wrong conclusion.

B.表示一种未实现的可能性，即本可以做某事，而实际上并没有做，有时含有抱怨的口吻。

It was a narrow escape.You might have killed yourself.

A lot of men died who might have been saved.

3)must have+过去分词

表示逻辑上的必然性，即按照某些现象推断过去肯定发生过的某事。

She must have made a big mistake.

The city at one time must have been prosperous,for it enjoyed a high level of civilization.

4)needn’t have+过去分词

表示过去不必做某事，但已经做了，即本可不必做某事。

You needn’t have woken me up.I don’t have to go to work today.

He needn’t have watered the flowers,for it is going to rain.

5)should/ought to have+过去分词

表示过去应该做某事而实际上没有做。

You should/ought to have done what your parents told you.(But you failed to do it.)

You should/ought to have been more careful.(But you weren’t.)

6)shouldn’t/oughtn’t to have+过去分词

表示过去不应该做某事而实际上却做了。

You shouldn’t/oughtn’t to have crossed the road when the lights were red.(But you did.)

They shouldn’t/oughtn’t to have left so soon.(But they did.)

7)would have+过去分词

表示对现在或将来某时之前业已完成的动作的推测。可译为，“可能”、“也许”、“想必”。

He would have arrived by now.

She would have recovered by then.