can...have
done/cannot
have done 表示对过去发生的行为的怀疑和不肯定通常用在否定句和疑问句中。(can换成could时语气较委婉) ①I can’t find him anywhere.Where can he have gone?can’t have finished reading the book so soon because it is difficult even to an adult.
could have
done 本来能够而没有做 (2017·高考福建卷)He could have gone on regretting it, 表示本来可能……但实际上没有发生的事情。 You should not swim in that sea.You might have been eaten by a shark.
should/ought(1)用于肯定句时表示本该做某事而实际上未做;(2)用于否定句时则表示不该做的事反而做了。 ①You shouldn’t have done it so carelessly.ought to have returned the book earlier.
③You ought not to have refused his offer.
needn’t
have done 表示做了本来不必去做的事没必要做而做了”。温馨提示 didn’t need to do表示“没必要做而实际上也没有做某事”。 ①You needn’t have brought the book because Tom has one here.didn’t need to buy the dictionary.I had a copy at home.
(2017·高考陕西卷) My book________ have taken it?
A.needB.must
C.shouldD.could
解析:选D。考查“情态动词+have done”的用法。句意:我的书《哈迪斯之屋》不见了。会是谁把它拿走了呢?need have done sth.本来有必要做某事而没做;must have done sth. 一定做过某事只用于肯定句中表示非常肯定的推测;should have done sth.本来应该做某事但实际上没做。根据句意D项could。
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