情态动词 语法讲解

“理所当然，有足够的理由”。 a. He has grown up tall. You may well not recognize him.

三、must, have to

１、表示义务和强烈的劝告。意思为“必须”、“一定要”。

a. You must finish your task ahead of time.

b. You must talk to your daughter about her future.

2、表示有把握的推测，意思为“一定是”，“准是”。

a. I failed in the exam. You must

9

think I am stupid.

He must be a college student, isn’t he?

b. You look happy. You must be having a good time.

c. He looks tired. He must have stayed up late last night, didn’t he? d. You speak English so fluently. You must have learned it for many years, haven’t you?

3、表示肯定性或难以避免，意思为“必然会、”“肯定会”。 a. All men must die.

b. Don’t bet o horse races; you must lose in the long run.

4、作“偏要”、“硬要”解。

10

（1）常以第二人称为主语，意思指不耐烦过令人不愉快的事情。 a. If you must smoke, at least you should do it outside.

b. If you must know, I’m going to help him look for an apartment. c. Why must you buy that car?

（2）用于其它人称，表示主语“固执”或“不巧”的意思。

a. The car must break down just as we were starting our holiday.

b. Jane was never a pleasant young girl. After you gave her your advice, she must go and do the opposite.

11

5、must的否定有如下三种形式，用于三种不同的场合。

(1) 当must表示“推测”时，其否

定含义为“不可能”。将 must be 改为 cannot be；将 must have done 改为 cannot have done。

a. It must be eleven o’clock now. It cannot be eleven o’clock. b. You must have met him before. You cannot have met him before. (2)当 must 表示“必须”时，其否

定含义为“不必”。将 must do

12