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1）must have done 过去一定做了某事,只用于肯定句。 2)can’t/couldn’t have done 过去不可能做了某事 3)could have done “本来可以……”（表示过去没有实现的可能）。 4)may /might have done “本来可能……；本来应该或可以做某事”（实际没有发生；含有轻微的责备语气。 5）should/ought to have done “本来该做某事”（而实际未做） 6)should not/ought not to have done “本来不该做”（实际却做过了，含有责备语气） 7)needn’t have done “本来不必做”（但是已经做过了） 8)would rather have done “当时宁愿做了某事”（实际没有做过）； 否定式would rather not have done, 表达相反意思“宁愿当时没有做某事”，两者都有后悔之意。 练习： 1. We have bought so much food now that Suzie won’t be with us for dinner. A．may not B．needn’t C．can’t D．mustn’t (2017江西) 2. I met Mr. White shortly after the Second World War, and that ___ about March 1946, I suppose. A. is B. maybe C. must have been D. may have been 3. My sister met him at the Grand Theater yesterday afternoon, so he ___ your lecture. A. couldn’t have attended B. needn’t have attended | 
