不對(duì).
must表示必須時(shí),
其反義疑問(wèn)句用needn't,
表示推測(cè)時(shí)用isn't或aren't后加主語(yǔ),
例如：He must be in the classroom, isn't he?
They must be at work, aren't they?
這兩句不能用mustn't.
用May引導(dǎo)的請(qǐng)求許可的句子否定回答方能用mustn't,
例如：A: May I come in?
B: Yes, you May. （肯定回答）
B: No you mustn't! （否定回答）