问题描述：
反意疑问句中的must
eg：It must have rained last night ,didn^t it
He must have finished the work ,hasn^t he?
为什么一个是didn^t 一个是hasn^t?
两句话must后都是完成时啊,或者说是didn^t和hasn^t 都可用?
eg：It must have rained last night ,didn^t it
He must have finished the work ,hasn^t he?
为什么一个是didn^t 一个是hasn^t?
两句话must后都是完成时啊,或者说是didn^t和hasn^t 都可用?
问题解答：
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