情态动词+have +done，表示推测与表示虚拟。 我只问张达人，网上的资料都不一样。
should have done/shouldn't have done
need have done/needn't have done
may(might) have done/haven't done
could have done/couldn't have done
would have done/wouldn't have done 展开
情态动词 + have done用来表示对过去情况的虚拟，用于不同的句式。
1、would、could、might、should 和 ought to 用在条件虚拟句中表示不同的意思，如：
They would have been killed if the car had gone over the cliff. 如果汽车当时翻到悬崖下, 他们早就丧命了。（would表示会有某种倾向性）
They could have been killed if the car had gone over the cliff. 如果汽车当时翻到悬崖下, 他们本可以丧命的。（could表示本来可以）
They might have been killed if the car had gone over the cliff. 如果汽车当时翻到悬崖下, 他们或许会丧命的。（might表示有可能某种量度）
They should have been killed if the car had gone over the cliff. 如果汽车当时翻到悬崖下, 他们本来就该丧命。（should表示按主观期望应该）
They ought to have been killed if the car had gone over the cliff. 如果汽车当时翻到悬崖下, 他们本来可能丧命了。（ought表示按客观条件应该）
2、must用于有把握的推测，may 用于无把握的猜测，如：
They must have been at home then. 当时他们一定在家。
They may have been at home then. 当时他们或许在家。
3、can/could 和 may/might 常用在目的状语从句。如：
I had stepped aside so that she might have come in. 我当时往旁边走一步，以便她能进来。
Double over the map so that we can read it moreeasily. 把地图对折起来，这样看起来更容易。
They flew there in order that they might be in timeto attend the opening ceremony. 他们飞往那里以便能及时参加开幕典礼。
4、should 还用于表示个人看法的名词从句中，不过常常省略，如：
I had suggest that he (should) have been there in time. 我本来认为他早应该按时到达那里。（宾语从句）
It was suggested that he (should) have been there in time. 有人曾提议他本应该按时到达那里。（主语从句）
My suggestion was that he (should) have been there in time. 我的建议曾经是他本应该按时到达那里。
5、need have done/needn't have done 在虚拟语气中不多见
还有人说情态动词+have done表示对过去的推测？我就是这个弄不懂。结合你的第二部分，我是理解了must have done与may have done，但是还有其他的情态动词例如can，could，真的好乱。
must 变成否定或疑问推测就需要用 can/could，如：
肯定： He must have gone then.
否定： He can't/couldn't have gone then.
疑问：Can/could he have gone then?
could 比 can 语气委婉。
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2023-06-12 广告
