they must be teachers怎么变成一般疑问句？ it must be .改为一般疑问句

they are teachers\u6539\u6210\u4e00\u822c\u7591\u95ee\u53e5\u548c\u5426\u5b9a\u53e5

they are teachers
\u6539\u6210\u4e00\u822c\u7591\u95ee\u53e5
Are they teachers?
\u6539\u6210\u5426\u5b9a\u53e5
They are not teachers.

it must be some bananas,aren't they?

这是一个含有情态动词must的句子，所以在变为一般疑问句时，只要把must提前即可，即:Must they be teachers?

Must they be teachers?

这个句子谓语出现情态动词must,根据英语语法规律，变成疑问句时需要把情态动词must调到句首，句末要用问号。

They must be teachers.
他们一定是老师。

一般疑问句直接把情态动词must提到句子开头。
Must they be teachers？

一般疑问句 Must they be teachers? 或者 Do they have to be teachers?