中考英语复习:2010中考英语重点语法词法考点十 情态动词

一．情态动词的用法
1. can 用法
1）表示能力，与be able to同义，但can只用于现在时和过去时，be able to可用于各种时态。
Two eyes can see more than one.
注：Can you … ? Yes, I can / No,I can’t.
2).表示允许、请求
用could比can 语气更加委婉客气，常用于could I /you …..?句型中，若表示同意时，用can回答而不用could .
Could I borrow the book ? No, you can’t .
3）。表示推测 “可能”常用于否定句或疑问句中。（can’t表示一定不是）
It can’t be true .
Can it be true ?
2. may 用法
1）表允许，请求= can
表示许可或征求对方的许可，常于第一人称连用。
注：May I ….? Yes ,you may No, you can’t / mustn’t .
在回答以may引起的问句时，多避免用这个词，而用其它方式，如Yes, please. / Certainly.
2）表推测，可能、也许。常用于肯定句中。
Maybe he knows the news .=
He _____ _____ the news.
3. must
1）表示义务。意为“必须”（主观意志）。
We must do everything step by step.
注：Must I ….? Yes, you must / No,you needn’t(don’t have to ).
--Must we hand in our exercise—books now?
--No, you needn’t. / No, you don’t have to.
2）mustn’t 表禁止、不允许。
You mustn’t talk to her like that.
3）表示揣测。意为“想必、准是、一定”等，只用于肯定句。否定、疑问句中must改为can .
He must be ill. He looks so pale.
She’s wearing a diamond necklace. She must have a lot of money.
注：must表推测时，其反义疑问句与must后面的动词一致。
There must be something wrong ,____ ____?
4.need的用法
need既可用作情态动词，也可用作实义动词。用作情态动词时，主要否定句或疑问句中。用作实义动词时，可用于各种句式。
1).用作情态动词，用于否定句和疑问句中。
a).Need I ….? Yes , you must / No, you needn’t .
Need we finish the work today ?Yes you __?
A.need B.can C. may D.must
b).need + do sth . 变否定句：needn’t do sth
变疑问句：Need sb do sth ?
2).用作实义动词
a).need + to do sth . We need _______(buy) some school things .
变否定句：don’t /doesn’t /didn’t +need to do sth .
变疑问句：Do / Does /Did sb + need to sth ?
Yes , … do/ does / did No, sb don’t / doesn’t /didn’t .
You don’t need to do it yourself.
b).当主语是物时。Sth + need + doing sth = Sth +need to be done .
The table needs painting . =The table needs _____ _____ _____ .
5.had better 的用法
1). had better + 动词原形 = It’s best to do sth .
You had better ______ (stay )at home . = _____ ______ ______ stay at home .
2). Had better not +动词原形
We had better ________(not play ) the computer games .
6.must 与have to
1).一般情况下，两者可互换。 must = have to
2).must “必须，应该”表示说话人的主观看法，即说话人认为必须干某事。（内在原因）
have to “必须，不得不”强调客观需要，即外界因素迫使某人不得不干某事。（外界原因）
I can’t stop playing the computer games . For your health ,I’m afraid you ______.
A.can B.may C.must D.had to
二．情态动词后跟完成式和进行式的用法
1.情态动词后跟完成式，表“原本应该干某事，而实际上没干”
I should have finished the work earlier.
He isn’t here. He must have missed the train.
2. 情态动词后跟进行式，表示“想必正在……”，“可能正在……”，“应当正在”等意。
It’s twelve o’clock. They must be having lunch.
They may be discussing this problem.
He can’t be telling the truth.
She shouldn’t be working like that. She’s still so weak.
三．情态动词的同义转换.
1.can = be able to
2.must = have to
3.needn’t = don’t have to
4.need do sth = need to do sth .