2022年教师招聘英语备考：动词三

2022年教师招聘英语备考：动词三
【动词(三)】
一、助动词
助动词本身没有词义，不能单独作谓语，只能和主要动词一起构成谓语动词，表示否定、疑问、时态、语态等语法形式，或用来加强语气。

常用的助动词有:be, do, have, shall, will等。

它们的具体用法如下：
(1)助动词be
A. 可用于构成进行时态
She is doing her homework now.
I asked him what he had been doing all afternoon.
B. 可用于构成被动语态
The baby was put in bed by his mother.
The invitation was received yesterday.
C. 可与动词不定式构成谓语
These books are not to be taken out of the room.
She is to arrive at six this morning.
(2)助动词have
A. 构成完成时态
I have not seen him for three years.
How long has your uncle taught in the village?
He had lived in Scotland for fifteen years before he came to England.
B. 和动词不定式构成谓语，表示因客观环境促使不得不做的事情
She had to go shopping yesterday.
(3)助动词do
A. 构成疑问句和否定句
Did anyone sharpen this knife?
I don’t think you are right.
B.用来加强语气
I do want to have a talk with you.
Do come and see me.
C.用来代替动词词组
Have you finished your work? Yes, I did yesterday.
He plays basketball well. So does his brother.
(4)助动词shall
构成将来时态，单纯表示未来情况
I shall not be back tonight.
(5)助动词will
构成将来时，用于第一、二、三人称。

如：
They will move to a new house.
She will not eat any solid food.
注意：
(1)have to 与must的区别
must是情态动词，意思是“必须”、“应该”、“一定要”，后接动词原形。

Must的否定形式为mustn’t.构成疑问句时，肯定回答一般用must。

否定回答用needn’t或don’t have to 表示“不必”。

如：
Must I do it now?
Yes, you must No, you needn’t.
have to 表示“不得不，必须”，可用于多种时态。

I missed the train, so I had to take a taxi.
I’m sorry I won’t go with you, I’ll have to go to the bank.
We don’t have to install this new television set.
(2)used to 表示过去常常，而现在不再有的习惯。

其否定形式为: used not to, usedn’t (usen’t) to, didn’t use to.
I used to go to work by bus. Now I go by car.
I used to collect stamps when I was a boy.
Used they to have a lot more free time?。