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1. could have + 过去分词

(1)表示对过去可能发生的事情的推测，意为“可能做了某事”。

He couldn’t have seen her yesterday.

They could have lost their way.

(2)表示某事在过去本有可能发生，但事实上并未发生，意为“本可以做某事”。

We could have started a little earlier.

I could have killed her. It was a narrow escape.

2. may (might) have + 过去分词

(1)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.

(2)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