must 是情态动词

表示：

Must I hand in my homework todayYes, you must. No, you needn't/don't have to

It's no parking area. You mustn't park your car here. Or you will receive a ticket.

例句：He must belong to the soccer club.

It must be Tony's bag. There is his name on it.

The man at the school gate can't be our headmaster. He is having a meeting in his office.