反意疑问句

题目

反意疑问句
一.我看我的初中英语语法书里面有一章是 反意疑问句
1.陈述语句的谓语动词含有must
c.must 表示推测意义,作“必定 准是”讲时,反意疑问句应根据陈述部分不定式结构选用相应的助动词
They must have finished their work,haven't they?
She must have gone out last night,didn't she?
我想问的是为什么这两句中的have都做现在完成时的助动词,为什么一个用have反问,而一个用did反问?
2.主语比较特殊的反意疑问句
c.当陈述主语是nobody everyone等不定代词时,其反意疑问句部分的主语既可以用复数代词they（与复数动词连用）,也可以用单数代词he（与单数代词连用）
Everyone likes Beijing,don't they?
我想问的是everyone是三单,反意疑问句用they提问吗?
这些句子均出自语法书,非本人胡编乱造.

答案

They must have finished their work,haven't they?She must have gone out last night,didn't she?第二句是有last night作为时间点的,针对那个时间点来提问只能用过去式啊.Everyone likes Beijing,don't they?我想...