They must have been to the USA,have not they?与He must have b
3个回答

你好,你没有搞懂这些句子的用法:

在这两个句子中,因为都没有时间状语的修饰,所以句子发生的时间不确定,答案也不确定,请你看以下的句子,

They must have been to the USA,haven't they?

He must have been to the USA,hasn't he?

这两个句子都是对的,因为都没有时间状语,可以翻译为:

他(们)到过美国,是吗?

但是加一个状语则变为以下的两个句子:

They must have been to the USA last year,weren't they?

He must have been to the USA last year,wasn't he?

因为,这两个句子都表示去年去了美国这个具体的时间发生的事,所以要用一般过去时态.

又如下面的这个句子:

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

It must have rained ,hasn't it?