They can't have been doing thier homework.have been 是现在完成时,但是后面do为什么要变成doing?They can't have been doing thier homework.这句话 have been 是现在完成时,但是后面do为什么要变成doing?为什么不用do呢?

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Theycan''thavebeendoingthierhomework.havebeen是现在完成时,但是后面do为什么要变成doing?Theycan''thavebeendoingthierhome

They can't have been doing thier homework.have been 是现在完成时,但是后面do为什么要变成doing?They can't have been doing thier homework.这句话 have been 是现在完成时,但是后面do为什么要变成doing?为什么不用do呢?
They can't have been doing thier homework.have been 是现在完成时,但是后面do为什么要变成doing?
They can't have been doing thier homework.这句话 have been 是现在完成时,但是后面do为什么要变成doing?为什么不用do呢?还有They must have been playing in the garden.为什么也用playing,而不用play呢,

They can't have been doing thier homework.have been 是现在完成时,但是后面do为什么要变成doing?They can't have been doing thier homework.这句话 have been 是现在完成时,但是后面do为什么要变成doing?为什么不用do呢?
现在完成时结构 have/has+P.P.
现在完成进行时结构 have/has +been+doing
此句在现在完成进行时 前加上情态动词,can't have been doing 表示一种语气较肯定的推测.意为那时不可能在做某事

LZ这叫现在完成进行时

can't have been doing 是情态动词表示推测，而且是对过去正在发生的动作表示推测，意为那时不可能在做某事。must have been doing表示那时一定在做某事，是对过去正在发生的肯定推测。这个语法点在新概念一册129课130课。

首先have been 后面绝对不可能接do 原型，要么是have done! have been doing 是现在完成进行时，但依据你说的句子，句中另有must ,所以应该是must have句型，表推测(此处表示对现在进行的动作推测)，所以最后是have been doing

这不是现在完成时，是现在完成进行时

They can't have been doing thier homework.
他们不可能一直还在做作业

表示对已经发生的事作以否定的推测，要用
can't have done
你你可能看过这部电影。 You can't have seen the film

如果过去发生的某个动作现在可能还在持续， 用：
can't h...

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They can't have been doing thier homework.
他们不可能一直还在做作业

表示对已经发生的事作以否定的推测，要用
can't have done
你你可能看过这部电影。 You can't have seen the film

如果过去发生的某个动作现在可能还在持续， 用：
can't have been doing
他们不可能还在等。 They can't have been waiting

注意： 如果是肯定推测， 就不可用can, 而用may, must(最有把握时用）
你可能看过这部电影。 You may have seen the film. (不用can)
你一定看过这部电影。 You must have seen the film.

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I think they were Canadian.I don't think they were.They can't have been Canadian.They must have been Australian.帮我看看有无语法错误 They can't have been doing their homework请问can't have been是对刚才所发生的事的推测吗? 用can't have been造句! Greens must have been to Shanghai ,_____they?A.hadn't B.didn't C.can't D.weren't还有haven‘t they They can’t have been doing their homework ---doing是什么词性?have been 在这里还是表现在完成时吗 They must have been enjoying themselves there,or they _____ so long.[A] can't have stayed [B]wouldn't have stayed [C] needn't have stayed [D] couldn't stay为什么选B?清翻译整句 They can't have been watching the football match this time yesterday,___?A.must theyB.can theyC.have theyD.were theywhy choose They can’t have been doing their homework--句中“can't是不是可以直接去掉,从语法上来讲没有错啊?还有They can’t have been doing their homework能改成：They haven't been doing their homework They can't have been doing thier homework.have been 是现在完成时,但是后面do为什么要变成doing?They can't have been doing thier homework.这句话 have been 是现在完成时,但是后面do为什么要变成doing?为什么不用do呢? (They must have been there yesterday ,______they?)能用weren't they 还是didn't they? 英语翻译A.can't have been B.mustn't have been C.shouldn't have been D.wouldn't have been can’t have been与couldn’t have been的区别? Where have they been? 1.She ( ) lived here for three years. 2.They can't spend that money, because it is not( ).1.A.have been B. didn't C.has been D.has2.A.theirs B.their C.they D.them can't have been和must have been每一个的用法 She can't have been Danish. and She must have been Swedish. be,must be,can't have been,must have been吗 must have been和can't have been和现在完成时有没有联系啊