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时间:2015-03-02 12:44:55
【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 91ExaM.org 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?
【 动 词(四)】
情态动词
(1)情态动词表示说话人对某一动作或状态的态度，或表示主观设想。情态动词有自己的词义，但不能单独作谓语动词，必须和不带to的动词不定式连用，没有人称和数的变化，常用的情态动词有can, may, must, will, shall, should, would, need, dare.
① 情态动词有自己的词义，表示说话人对某一动作或状态的态度，或主观设想。如：
You may go now.
This bus can seat 40 people.
The work must be finished as soon as possible.
② 情态动词不能单独作谓语，必须和不带to的不定式连用，没有人称和数的变化。
③ 情态动词有现在式和过去式两种形式。
(2)情态动词的用法。
① may的用法
a. 表示允许或征询对方的许可，有“可以”的意思。May not表示说话人“不许可”，如：
You may go now.
May I use you typewrite?
You may not go=I do not permit you to go.
b. 在回答may引导的疑问句时，肯定回答用yes, you may否定用No, you mustn’t. No, you can’t或No, you had better not.
② can的用法
a.表示能力，有“能、会、能够”的意思。
b. 表示允许，在口语中代替may，有“可以”的意思。
c. 表示“可能性”，常用于否定句或疑问句。
The hall can hold at least 200 people.
The libra rian said we could take these books.
Today is Sunday, he can’t be at school today.
d. can和be able to的用法比较
can用来表达能力时，由于只有现在时和过去时两种形式，其他时态要用be able to来表达。如：
I can play the piano.
He has not been able to finish the work in time.
③ must 的用法
a. must表示必须，应该。如：
Must I come to the party?
The article must be completed before Friday.
b. must的否定形式mustn’t, 表示“不应该、不可以、禁止”。如：
You mustn’t get to school too late.
Must I do it now? Yes, you must. No, you needn’t
She must have gone to Beijing.
You must say sorry to me for that.
You mustn’t clean only your own room.
④ need的用法
a. need作为情态动词主要用于否定句和疑问句，较少用于肯定句。如：
I needn’t wear a coat. = I don’t think I need wear a coat.
I don’t need things like that.
⑤ shall
用于第二、第三人称，表示说话人的意愿。如:
He shall get his money.
You shall do exactly as you wish.
Sh all I turn on the light?
Shall I open the window?
⑥ would的用法
表示愿望、决心、建议或看法，如：
I would like to go there.
I promised that I would do my best.
表示过去的习惯.
He would often come to my house to see me.