Must I ...? (我必须。。。)
- Yes, you must. (是的,你必须。。。)
- No, you needn't. (不,你没必要。。。)
May / Can I ...? Yes, you may/ can... No, you may not../ can't...
否定回答是no,you can‘t或者may not。一般的needn't是回答must的