英语语法知识难点（三）

（十）情态动词与助动词

I． 要点

助动词本身无意义，在句中帮助主要动词构成一定的时态，语态、语气，或是帮助构成否定句和疑问句，常用的助动词有be, do, have, shall(should), will(would).

情态动词表一定的词义，本身并不表示动作或状态，而仅仅表达说话人的态度，它在句中须和主要动词一起构成谓语，主要的情态动词有can(could), may (might), must, have to, ought to, need, dare, shall, should, will, would.

1、can 能，可以，表说话人同意，许可还可表客观条件许可，如:You can go now.

提建议或请求时可用can I, can you表客气，如Can I buy you a drink?

can和be able to表能力时的区别。

can表一般具有的能力，be able to表在特定条件下的能力，如:Although the driver was badly hurt, he was able to explain what had happened.

2、may

（1）、可以，表说话人同意，许可或请求对方许可。You may go.

（2）、（现在和将来）可能，也许，只用于肯定句和否定句中，如He may not be right.

3、must, have to

must表主观上的必须，have to表客观上的必须，如:It's getting late. I have to go. -Must I go now. -Yes, you must.

(No, you needn't./ No, you don't have to.)

4、need, dare这二词有实意动词和情态动词两种词性，如用作实意动词后接动词不定式to do，如用作情态动词后接动词原形。Need I go now? --Yes, you must./No, you needn't.)

5、shall用于第一人称疑问句中表说话人征求对方的意见或向对方请求，如，Shall we begin our lesson?

用于二、三人称陈述句，表说话人命令、警告、允诺、威胁等口吻，如: You shall fail if you don't work harder.

6、should表应该，意为有责任，有义务。如:We should try our best to make our country more beautiful.

7、will表有做某事的意志、意愿、安心、打算，如 "Will you lend me your book?" "Yes, I will."，

8、should have done表应该做而未做

must have done表对过去事实的肯定推测

could have done表本可以做某事

9、判断句：肯定句用must, 否定句用can't, 不太肯定用may, might

He must be in the office now.

He must have gone to bed, for the light is out.

He can't be in the office. He is at home.

He couldn't have cleaned the classroom, because he didn't come here today.

He might be in the office, I am not sure.

He might have cleaned the room, I suppose.

II． 例题

例1，They _______ to walk in the street at might.

A. didn't dare B. not dared C. not dare D. dared not

解析，该题答案为A， 此空需选一动词作谓语，因为后面是to walk, didn't dare是行为动词dare过去时态的否定形式。

例2，When he was very old, Mr. Smith _______ sit for hours without saying a word.

A. would B. should C. must D. used

解析，该题答案为A, would此处表过去的倾向性，习惯性动作，意为"总是"如: When we were children, we would go swimming every summer.

（十一）句子种类

I． 要点

句子按使用目的可分为陈述句、疑问句、祈使句和感叹句；按结构又分为简单句、并列句和复合句。

1、陈述句的否定

（1） 在含有宾语从句的主从复合句中，当主句的谓语动词是think, expect, believe, suppose, guess, fancy, imagine等，且主句主语是第一人称时，宾语从句谓语的否定习惯上要移到主句谓语上，如: I don't think he is right.

（2） 含有否定意义的副词never, seldom, hardly, scarcely, rarely, barely的句子应视为否定句，如: I have never been there before.

2、反意疑问句

（1） need和dare 既可作情态动词，又可作实意动词，在反问部分须加以区别，如We needn't leave, need we? We don't need to leave, do we?

（2） 陈述部分出现否定意义的副词或代词如never, seldom, few, hardly, little等时，反问部分须用肯定形式如：He seldom comes, does he?

（3） 陈述部分用不定代词作主语时，反问部分的主语用it ，如：Nothing can stop me, can it?

陈述部分用everybody, everyone, somebody, someone，等作主语时，反问部分常用it，有时也用they，如:Everybody knows that, don't they?

（4） 陈述部分包括used to 时，反问部分可有两种形式，如: You used to get up early, usedn't (didn't) you?

（5） 陈述部分是"there + be"结构时，反问部分用there，如:There's something wrong with you, isn't there?

（6） 陈述部分是含有宾语从句的主从复合句时，反问部分的主语和谓语应和主句保持一致，如: He never told others what he thought, did he?

但，如果是I think , I believe等 +宾语从句时，反问部分须和从句的动词保持一致，如，I don't think he is right, is he? I don't believe he does that, does he?

3、感叹句

用what或how,

What a beautiful park it is.

How beautiful a park it is.

How beautiful the park is.

How we worked!

4、祈使句

Take care!

Don't stand there.

Please open the door for the old lady.

II．例题

例1，Don't forget to post the letter, _______ ?

A. will you B. do you C. won't you D. shall you

解析：该题答案为A， 在否定句、祈使句后只用"will you"?，但肯定的祈使句后可用如，Wait for me, will (won't, can, can't, could) you?

例2，Let's go out for a walk, _______ ?

A. will you B. won't you C. shall we D. do we

解析：该题答案为C，let's…后加上shall we来表语气婉转、客气，而在let us后加上will you。

例3，He hardly writes to you, _______ ?

A. doesn't he B. does he C. do they D. has he

解析：该题答案为B，hardly否定副词，反问部分要用肯定形式。

（十二）各种从句

I．要点

根据从句在句中的句法功能，从句可分为名词性从句、定语从句和状语从句。

1、 名词性从句

（1） 主语从句

What he wants is a piece of paper.

It is believed that he can solve the problem.

注：主语从句的谓语动词用单数。

（2）宾语从句

I don't know how to solve the problem.

Do you know where he lives?

（3）表语从句

The problem is who can help me.

This is why I came here.

（4）同位语从句

I have no idea where he went.

I heard the news that he would come.

同位语从句用that引导，常跟在fact, idea, news, promise, thought, message, hope, belief, doubt等词后，that在从句中不作任何成分。

2、定语从句

在复合句中，修饰某一名词或代词，或修饰整个主句的从句叫做定语从句，引导定语从句的关系代词有who, whom, whose, which, that, as,和关系副词when, where, why。

（1）that指物时一般可与which互换，但在下列情况下，要用that而不用which。

a. 先行词有all, everything等不定代词时，如，

Everything (that) he did is wrong.

b. 先行词被all, every, no, some, any, little, much等修饰时，如，

I'll read all the books (that) you lend me.

c. 先行词被序数词或形容词最高级修饰时，

This is the first letter (that) the boy has written.

d. 先行词被the only, the very, the same, the last修饰时，如

He is the very man (that) I'm looking for.

e. 只用which的情况

在介词后或在非限定性定语从句中

This is the book about which we have talked a lot.

The book, which he gave me yesterday, is very interesting.

f. where和when作关系副词

This is the room where I worked.

This is the room which I stayed in.

I remembered the day when we lived there.

I remembered the day that I spent there.

g. as和which

as 可以放于句首，而which 不可以

As you know, he is good at English.

three of them 和three of which

I have a lot of books, three of which are in Russian.

I have a lot of books and three of them are in Russian.

3、状语从句

在复合句中起状语作用的从句叫做状语从句。状语从句可分为时间状语、地点状语、原因状语、目的状语、结果状语、条件状语、行为方式状语、比较状语、让步状语等多种。

II． 例题

例1、 _______ I accept the gift or refuse it is none of your business.

A. If B. Whether C. Even if D. No matter when

解析：该题答案为B。whether可以和or连用，if不可以，此外if一般仅用于宾语从句。

例2、The way _______ these comrades look at problems is wrong.

A. where B. in that C.X D. with which

解析：该题答案为C，先行词是way，定语从句中用that或 in which来引导或不填。

例3， ____a long time since I saw you last time.

A．It was B. It is C. It had been D. It can be

解析：该题答案为B，It is +时间数+ since引导的从句是一个句型，意为"从…时候以来过了多久了。"

（十三）主谓一致

I． 要点

谓语受主语支配，须和主语在人称和数上保持一致，这叫做主谓一致，主谓一致包括语法一致、意义上一致和就近一致。

1、语法上一致

（1）、以单数名词或代词，动词不定式短语、动名词短语或从句作主语时，谓语动词要用单数，主语为复数时，谓语用复数，如，

To work hard is necessary for a student.

（2）、用and或both……and连接的并列主语，谓语动词用复数，如，

Both he and I are right.

但并列主语如果指的是同一人，同一事物或同一概念，谓语动词用单数，如, His teacher and friend is a beautiful girl.

（3）、主语是单数时，尽管后面跟有as well as, but ,except, besides, with ,along with, together with, like等，谓语动词仍用单数，如，

The teacher as well as his students is excited.

（4）、某些不定代词，如做主语，谓语动词要用单数，如:Everyone has a book.

（5）、一些只有复数形式的名词，如people, cattle, clothes等作主语时，谓语动词要用复数，如，A lot of people are dancing outside.

2、意义上一致

（1）、表时间、距离、价格、度量衡等的名词作主语时，谓语动词通常用单数，如，

Twenty years is not a long time.

（2）、表示总称意义的名词public, police, cattle, clothes等作主语时，谓语动词用复数，如，

People are talking about the accident.

（3）、有些集合名词，如family, team等作主语，如作为一个整体看待，谓语动词用单数，如指其中每个成员，则用复数，如，

My family is a big one.

My family are watching TV.

3、邻近一致

用连词or, either……or, neither……nor, whether……or, not only…but also,等连接的并列主语，如果一个是单数，一个是复数，则谓语动词按就近一致原则，与最靠近它的主语一致，如，

Either you or I am mad.

II．例题

例1、 The chemical works _______ where my father has worked for thirty years in 1949.

A. was built B. were built C. is built D. are built

解析：该题答案为A。works形式上是复数，意思上是单数，因此谓语动词用单数，类似的还有news, maths, politics, physics.

例2、They each _______ a copy of the new physics.

A. have B. has C. having D. gets

解析：该题答案为A。They each不等于each of …, each of 这个词组作主语谓语用单数如each of the students hands in their homework，而they each作主语，谓语要随each前面的词来变化。

英语语法知识难点（四）

（十四）倒装

I．要点

按"主语+谓语"这种顺序排列的句子是陈述语序，如果变为"谓语（或谓语的一部分）+主语"，就是倒装语序。

1、全部倒装

（1）there be 句型

There is going to be a meeting.

There is a book on the table.

（2）here, there, now, then, in, out等副词置于句首时，主谓倒装，但如果主语是人称代词时，主语和谓语语序不倒装，如，

Here comes the bus.

Here he comes.

（3）直接引语的部分或全部位于句首时，有时也用倒装，如，

"What he said meant nothing", said the teacher.

（4）为保持句子平衡，强调表语或状语，使上下文紧密衔接时须完全倒装，如，In front of the house sat a small boy.

2、部分倒装

（1）so, neither, nor置于句首说明与前者情况一致时，如，

I like swimming, so does my brother.

（2）only +状语放在句首，如，

Only through this method can we win.

Only in this way can we do the work well.

（3）含有否定意义的词置于句首，如，Hardly, scarcely, not, seldom, no sooner, never, little, at no time, in no way, no more等，如，

Never had I heard that.

Little did I know about this.

（4）以often, so +形容词或副词开头的句子，如，

So heavy is the box that he cannot carry it.

（5）用于省略if的虚拟条件句中，将had, were, should提前，如，

Were I you, I wouldn't do that.

Had he come, we would have won.

（6）用于某些表示祝愿的句中，如，

May you be happy for ever.

II．例题

例1、Not only ____ this machine but ____ it.

A. can he run……can he repair B. can he run……he can repair

C. he can run……he can repair D. he can run……can he repair

解析：该题答案为B，在not only……but (also)句型中，只有but前面的部分倒装，but后面仍是正常语序。

例2、____, it is quite easy to drill a hole in it with laser（激光）.

A. Hard although the diamond B. Hard as the diamond is

C. As the diamond is hard D. Has hard is the diamond

解析：该题答案为B，在让步状语从句中，从属连词as可以表示though，但要用倒装语序。

例3、Only in this way ____ to improve the situation there.

A. can you hope B. you can hope C. hope can D. you hope

解析：该题答案为A， only和它所修饰的状语一起置于句首时，须用倒装。

（十五）it 与there be的用法

I．要点

1、it的用法

（1）用作人称代词，代替前文提到的无生命的事物，动植物、婴儿及指示代词this, that，如，

I have a new pen. It is beautiful.

The Browns have a new baby. It's cute.

（2）用来表示时间、天气、距离等，如，

It's twelve o'clock now.

It's fine today.

（3）用作引导词，代替由不定式，ing形式或从句表示的真正的主语或宾语，如，

It's no good telling him that.

It's necessary for you to do so.

（4）用在强调结构中，构成强调句式：It is/was +被强调部分+that/who/whom +句子其余部分，可强调除谓语以外的句子其他成分，如，

It was this morning that I saw him in the street.

It was I who saw him in the street this morning.

It was in the street that I saw him this morning.

It was him whom I saw in the street this morning.

2、there be句型

英语表示某时某处或某物时，常用there be句型，这是一种倒装结构，如，

There are a lot of students playing on the ground.

There is going to be a test this afternoon.

当主语有两个或两个以上时，动词be常和最近的那个主语取得一致，如，

There is a pen and three pencils in the pencil-box.

There isn't a desk, a bench and three chairs in the room.

There are lots of people like it, aren't there?

there be句型，谓语动词除be之外，还可用其他表示存在，位置移动等意义的不及物动词或词组，如exist, stand, lie, enter, come, happen to be, appear to be等，如，

There stands a house at the foot of the hill.

there be句型表示"存在"而have表"有"、"拥有"，所以there be中 be不能换成have，但当have表示事物的特征时，可用"主语+have"结构替换there be 句型，如：

There are five doors in the house.