It is in the library,you _______ talk loudly.

问题描述:

It is in the library,you _______ talk loudly.
A.may not B.can’t C.needn’t D.mustn’t
答案给的是D,可是B为什么不行呢?

It is in the library,you _______ talk loudly.
A.may not B.can’t C.needn’t D.mustn’t
选D
因为在图书馆小声说话是一项规定,所以是必须要执行的,用mustn't
can't表示不能,是指的一种能力