traffic regulations.
A. can B. shall C. may D. could
5. must/ have to a. 表示必须
You must come to school in time．
回答must引出的问句时，如果是否定的回答，不能用mustn't，而要用needn't或don't have to。
mustn’t表示禁止，不可以
Must we hand in our homework?
--- Yes, you must.
--- No, you needn’t./ No, you don’t have to. b. 表示肯定地猜测 It must have rained last night.
My mother must be having breakfast.( 表示对正在进行的动作的猜测), isn’t she? My sister must be at
home.(对现在的状态进行猜
测), isn’t she?
My mother must stay at home now, doesn’t she? He must have gone to bed, hasn’t he？
It must have rained last night. ( 表示对已经发生过的事情的猜测)，didn’t it? He must have been there the day before yesterday, wasn’t he ?
c. 硬要，一定要，非得要
If you must know, I am 18. Why must it rain at the weekends?
d. must 与have to 的异同 have to的含义与must相似，两者往往可以互换使用，但must与have to有下列几点不同：
①must表示的是说话人的主观看法，而have to则往往强调客观需要。如：
The film is not interesting．I really must go now．