eg. I can’t find my key, I might have left it at home. He might not have got your
letter.
5.ought to/should have done,”表示本应该 做某事，而事实上并没有做”。
否定句表示“ 本不该做某事而实际上做 了”。
你在实验中本应该更仔细些的
You ought to/should have been more careful in this experiment. 他不应该把那些旧衣服扔了。
He ought not to have thrown the old clothes away.
6. “needn’t have done”表示“本没 有 必要做某事实际上却做了” 这次旅行我穿太多了，我本没有必 要这样做，天气太热了。 I wore too much for the trip，but I needn’t have done so.The weather
was hot.
二.“情态动词+have done” 的用法。 1.must have done “过去一定做了某事” 表示对过去的一种肯定性推测。 eg. She must ast night, for the road is quite muddy.
3. “can/could not ＋have ＋done”“过去 不可能做了某事” 她不可能去你家，她不知道你的地址。 eg. She can not have been to your house；she does not know your address.
4. may/might have done“过去或许做过 某事” may/might not have done “过去或许 没有做过某事”
表推测的情态动词PPT课件
一. 表推测的情态动词有： 肯定的推测一般用must，should/ought to, may/might或could(不用can) 1.must的语气最强，译为“肯定， 准 是，想必是”；(mustn’t 表示禁止） 2.should/ought to 的语气次之，译为 “很可能, 应该”,指按常理推测； 3.may/might,could的语气最弱，译为 “也许，可能”。
4.can’t /couldn’t 表示否定推测, ‘‘不可
eg. You have been working hard all day ,you must be tired. He must be working in the office now. He should come here today. Can this be done by him? She may be still waiting for us. This may not be done by him. This can not be done by him.
2. can/could have＋done“过去可能 做了某事”， “could have＋done”也可表示‘‘过
去本可以做某事但实际上却没有做” eg. He was not at home last night, he
could have gone to the cinema. I could have finished my homework last night, but I was too sleepy.