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初中反义疑问句You must have made a mistake,haven’t you?  They must

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初中反义疑问句
You must have made a mistake,haven’t you?
  They must have seen the film last week,didn’t they?
为什么同样是表推测的完成时,第一个用have,第二个用did
初中反义疑问句You must have made a mistake,haven’t you?  They must
请看下面的说明:
当must后接完成式(即must + have + 过去分词),作“一定已经”讲,表示对过去的推测时:
a.若有表示过去的时间状语,则疑问部分用didn’t / wasn’t / weren’t提问.如 She must have been here yesterday,wasn’t she?/ You must have met her this morning,didn’t you?
b.若没有表示过去的时间状语,则疑问部分用haven’t / hasn’t提问.如 He must have been to Beijing,hasn’t he?/ The dogs must have eaten the food,haven’t they?
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