They must have done their homework yesterday,____?

4个回答

  • must have done 表示的是对过去动作进行推测,其反义疑问句的构成有两种:didn't .../wasn't(weren't) .../haven't(hasn't)...这两种形式的选择取决于句子中的时间状语.比较一种简单的方法是:不把它看成是推测,就把它看成是一种事实.

    比如:He must have been to Beijing,hasn't he?

    You must have been late for school yesterday,wasn't you?

    换句话说,用过去时还是用现在完成时来进行反问的区别,等同于过去时和现在完成时的区别.

    又如:It must have rained last night,didn't it?