mustn't等于什么

Question

请问mustn't等于哪个短语或单词呢？
we mustn't smoke here（保持句子原意）
we _____ _____ to smoke here.
请问这题怎么做？
额，all have to 对吗？

Answer 1

mustn't=must not 一定不能，must 的否定简写
You mustn't go to school late.你一定不能上学迟到

Answer 2

must not
we all have to smoke here.

Answer 3

must not