If must means "must" or "must", use must not or done not in the question part.

You have to leave at once, don't you?

You must leave at once, mustn't you?

However, if there is a mustave not in the statement, it means no, and the problem part should be must.

You can't laugh, can you?

You can't laugh, okay?

(2) If "must" means speculation, the question part cannot be "must", and the corresponding verb form should be adopted according to the verb structure after "must".

He must be tired, isn't he?

He must be tired, isn't he?

③ When "must" is used to express "must+done" in the past, such as emphasizing speculation about the past (there is an adverbial of past time in general sentences), antonym questions should use "no+subject"; If you emphasize the completion of the action (generally there is no past tense adverbial), you should use "have' t/hasn t+ subject" in the question.

She must have read the novel last week, didn't she?

She must have read the novel last Monday, didn't she?

You must have told her about it, haven't you?

You must have told her about it, didn't you?