They must have done their homework yesterday,___?为什么是didn't they?我觉得应该是haven't they啊?

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They must have done their homework yesterday,___?为什么是didn't they?我觉得应该是haven't they啊?
They must have done their homework yesterday,___?
为什么是didn't they?
我觉得应该是haven't they啊?

They must have done their homework yesterday,___?为什么是didn't they?我觉得应该是haven't they啊?
must have done :对过去事实的推测,不是现在完成(后者不能与明确的过去时间连用).反义问句是问“昨天他们是否做了家庭作业”,当然用didn't they.
比较:
They have done their homework,haven't they?
They did their homework yesteday,didn't they?

我也觉得是haven't they,复数怎么是用didn't勒

当must 表示对未知事情的推测时,构成反意疑问句,应根据 must后面的动词变化反意疑问句的提问词 如 :You must be tired ,aren't you ?

这里的have 是实义动词不是情态动词。只有在表示“不得不”做什么即“HAVE TO DO”时才用HAVE