can’t 和may not 有何区别?

can't 和may not 有何区别?
--Will they go for an outing today?
--Yes,____ because it seems that the weather is not so fine.
A.mustn't B.can't C.needn't D.may not
该选哪一个?为什么?麻烦举例说明.
对不起,打错了.应该是：
--Will they go for an outing today?
--They____ because it seems that the weather is not so fine.
A.mustn't B.can't C.needn't D.may not

A B D 在进行疑问回答的时候都是带有推测语气的,must 在表示推测的时候只用在肯定句当中 can在表示推测的时候多用与否定推测当中,而may 即可用于肯定推测,也可以用于否定推测.mustn't----一定不可以怎么样 may not---- 也许不(推测时不太有把握)can't ------不可能(推测时很有把握)needn't-----不必,在这个句子中说不通
这道题选D
给你举几个例子来说明
She may not be at home.=It is possible that she is not at home.
她也许不在家
She can not be at home.=It is impossible that she is at home.
她不可能在家.
下面我说一下must与 need not的关系
用must提出的句子,否定回答用needn't
如Msut I go now?No,you needn't.
即使改过来,答案也是D