情态动词must 的用法
1.must 表示必要性，“必须”（肯定句，疑问句常见）
Must I start at once?
例题
你必须现在睡觉。_________________.2.否定式mustn't 表示“禁止”例题
不许我们再迟到了。_________________3.由must 引导一般疑问句时，肯定回答用must，否定回答用needn't 或don't
have to.
---- Must I stay at home?
---- Yes, you / No, you _________________.___4.当出现反问句式时，如果其陈述部分must 表示“必须，有必要”时，反问句用needn't，如果其陈述部分mustn't 表示“禁止”，反问句用must.
例题
①----You must go there, you?
______---- Yes, I must. / No, I needn't/don't have to.
②You mustn't go there, you?
_________5.must 表示推测时，有3种形式时，反问句与must 后的动词保持一致。
⑴对现在的动作进行推测
①You must be hungry now, aren't you?
t you?
't/ don'You must have the wrong number. There is no such person, haven ②．
⑵对正在进行的动作进行推测
He must be doing his homework, isn't he？
⑶对过去发生的动作进行推测
①You must have read this book, haven't you?
②It must have snowed yesterday, didn't you?
6.must 用于反语，表示劝诫。
-----Must you make so much noise?(你非得吵这么大声吗？)
-----Sorry, I'll try not to.
例题
John, look at the time, ___ you play the piano at such a later hour?
A. must
B. can
C. may
D. need
与说话人的愿望相反，“偏偏，偏巧”。7.