情態動詞后接完成式

■表示對過去情況的推測

1. must have +P. P. 一定已經

2. can/could have + P. P. 可能已經

3. may/might have + P. P. 或許已經

用例：

He must have taken the book since it isn’t here. 他一定是把書拿走了,因為書已不在這里了。

What could have become of him now? 現在他可能怎么樣了呢?

You may have noted that my address has changed. 你也許已經注意到我的地址變了。

She might have gone to have her hair waved. 她可能去燙發去了。

注意：could have done還可表示“簡直就要”。如：

I could have died laughing. 我簡直要笑死了。 

■表示輕微的責備或后悔

1. ought to /should + have + P. P. 本來應該做某事(而實際上沒做)

2. ought not to /shouldn’t + have + P. P. 本來不應該做某事(而實際上卻做了)

3. could + have + P. P. 本來能夠做某事(而實際上沒做)

4. might have +P. P. 本來可以做某事(而實際上沒做)

5. needn’t + have + P. P. 本來不必做某事(而實際上做了)

用例：

I ought to have helped her，but I never could. 我本該幫助她的，卻從未能這樣做。

They oughtn’t to have let you out of hospital so soon. 他們不應當讓你這樣早出院。

We all know what the poor man should have said. 我們都知道那位可憐的人兒本來應該怎樣說。

You shouldn’t have told him about it. 你本不該把這件事告訴他的。

She could have applied for that job, but she didn’t. 她本可以申請這份工作的，但她沒有。

注意：其中could, might不可用can, may代替，這與表示推測時的用法不同。