A:Did you climb to the top of the Statue of Liberty when
you were in New York?
B:No,I didn't. My knee was very sore,and I____climb all those stairs.
(a)might (b)couldn't (c) must not
这题must not 为什么不能用?

You must not talk. 你绝对不能（不准）说话。怎么可能是用它咧？助动词就几个而已，每个的意思其实差蛮多的，多看几遍，多找例句吧！

其实也我知道他意思不一样啦，因为课本有说他还有逻辑跟否定的意思，所以我才在想说 他是否能选