2018年公共英语四级重点语法资料：表推测的用法
表推测的用法
1、must have done
表示对过去某事的肯定猜测，译为：过去肯定做了某事。不存在mustn’t have done的形式。其否定或疑问形式须用can(could)来表示。例如：
Since the road is wet, it must have rained last night.既然路是湿的，那昨天晚上肯定下雨了。
He can’t have missed the way. I drew him a map.他不可能迷路。我(当时)给他画了张图。
2、may/might have done
May/might have done表示“过去可能做了某事”。may比might 表示的可能性在说话人看来稍大些。may/might not have done表示“过去可能没有做某事”。例如：
I can’t find my keys. I may/might have left them at the school yesterday.
我找不到我的钥匙了。我可能昨天把他们落在学校了。
John may/might not have passed the exam, he looks very sad.
John可能没有通过考试。他看起来很忧伤。
注意：may/might have done表推测不能用于疑问句中。
3、can/could have done表推测，一般用在否定句和疑问句中，表示不相信或怀疑的态度。
Can/Could he have passed the exam?他可能通过考试了吗?
I think that he couldn’t/can’t have gone abroad. I saw him just now.
我认为他不可能出国了。我刚才还看见他了。
注：表示推测过去某动作发生的可能性是，就表示的可能性程度而言，must最大，could其次，may更次之，might最小。例如：
I wonder how Tom knew about your past.我想知道Tom是怎么知道你的过去的。
He must/could/may/might have heard of it from Mary.
他肯定/很可能/可能/也许已从Mary那儿听说此事了。
5、动词不定式
1、不定式做主语一般表示具体的某次动作。
To complete the 30-storied building in one year was quite a difficult task.
To do that implies taking responsibility.
当主语较长，谓语较短时，常用it做形式主语，而将不定式放到谓语的后面。如：
It is important for modern young people to master at least two foreign languages.
It做形式主语，不定式放在谓语动词之后常用于下列结构中：
A. It is+形容词+(for/of sb.)+不定式，如：
It is not easy to catch fish with your hands only.
It is important for us young people to learn English and master it.
B. It is+名词+不定式
It is a pity to have to go without her.
C. It takes (sb.) some time +不定式
It takes me three hours to learn English each day.
2、不定式作表语
不定式作表语常表示将来的动作，主语常常是表示意向、打算、计划的词(idea, task, purpose)等,如：
The most important thing for one’s health is to have plenty of exercise.
3、不定式作宾语
I like to go out for walks in the warm sunshine in spring.
She failed to finish the assignment in time, and she was worried about it.
4、“wh-+不定式”结构
不定式前加一个疑问代词(what, which, who, whom, whose)或疑问副词(where, when, how, why)，以及连词whether构成特殊的不定式短语，其作用相当于一个从句，这样的不定式短语常常在某些动词后面作宾语。
I couldn’t decide which book to choose.
I can tell you where to get this book.
“wh-word+不定式”结构除了作宾语外，还可以在句中作主语或者表语。如：
When to start the program remains undecided.
The question is how to put the plan into practice.
5、不定式作状语
A.不定式作状语表示目的。或用于so as和in order之后，来强调这种目的。如：
To learn a foreign language well, you must make painstaking efforts.
B.不定式表示结果，特别是在so…as to, such…as to, only to…以及too…to等结构中的不定式表示结果。如：
She left her hometown with her beloved man, never to return.
No one is too old to learn.
Would you be so kind as to carry the luggage for me?
C.不定式常用来修饰形容词，构成词组，如：
It is likely to rain today, for it is very cloudy.
I am willing to help you with your homework, for we are friends.
6、不定式作宾语补语不定式长跟在动词之后作宾语补语，如：
He asked you to call him at ten o’clock.
I’d never allow my children to behave like that.
当不定式在let, make, have, 感官动词后面作宾语补语时，不定式不带to。如：
Whenever something is wrong with you, please do let me know.
I will have the students write a passage about Internet.
7、不定式作定语
A.不定式作定语通常要放在其所修饰的名词或代词之后。不定式常作名词定语，如：
His efforts to carry out the plan were successful.
There is no need to bother him with such trifles.
B.由only, last, next, 序数词或形容词最高级修饰的名词常用不定式作定语。如：
Mr Zhang is always the first man to arrive at the office and the last man to leave.
I don’t think he is the best one to do the work.
8)不带to的不定式在下列词组后面的不定式不带to：
would rather…than(宁愿…也不)，had better…(最好)，can’t help but…(不得不)，had rather…(宁愿)，cannot but…(不得不，必然)，may/might as well…(不妨)，let alone(更不用说)。如：
I can’t help but wish that nothing would go wrong.
They had never seen such delicious food, let alone eat it.
9)不定式的完成式to have done表示在谓语动词之前已经发生的动作，而不定式的一般式to do表示动作将要发生。不定式还有其被动形式：to be done(表示将来的被动动作)和to have been done(表示过去的被动动作)。
6、动名词
1、在某些动词后面只能用动名词，如：
He hasn’t finished reading the novel. 他还没有看完那部小说。
We must practice speaking English. 我们必须练习讲英语。
2、 某些动词后接动名词与接不定式意义不同。如：
He stopped singing.他停止唱歌。 She tried pushing the door.她试着推门。
He stopped to sing.他停下来去唱歌。 She tried to push the door.她试图把门推开。
She remembered posting (having posted) the letter at the post-office.
她记得在邮局寄了那封信。
She remembered to post the letter at the post-office.
她记得要在邮局寄那封信。
3、 下列短语中的to是介词，其后跟动名词，不跟不定式。
be(get) used to 习惯于;look forward to 盼望;pay attention to 注意;get down to 开始认真做;lead to 通向、导致;prefer doing…to doing… 宁愿做…而不愿做…;stick to 坚持;devote one’s life(time, oneself) to 献身于、致力于;object to 反对;in addition to… 除…之外;on the way to… 在去…的路上、正要成为…
4、 在动词need, want, require后面，用动名词的主动形式表示被动的意义。用不定式时要用它的被动形式，如：
The house needs repairing. 房子需要修理
5、 be worth后面的动名词用主动形式表示被动含义，如：
The book is worth reading. 这本书值得读一读。
6、 一些动词短语如feel like, can’t help等后需要接动名词，如：
I don’t feel like going to see a film. 我不想去看电影。
The child couldn’t help laughing when he saw the monkey.这孩子看到猴子不禁笑了起来。
7、 动名词除了其一般式doing，还有完成时having done以及一般式的被动形式being done和完成式的被动形式having been done;动名词前可以加上逻辑主语，构成动名词的复合结构：one’s doing。例如：
I’m sorry for not having kept my promise. 非常抱歉，我没能遵守诺言。
(not having kept my promise发生在am sorry之前)
Do you mind Mary being left alone at home? 你介意Mary被单独一个人留在家里吗?
7、主谓一致
1、主语是抽象概念短语或从句作主语时，谓语用单数形式。
Collecting stamps is my favorite hobby.(动名词短语作主语)
That we have made such progress is a fact.(从句作主语)
2、what或which引导的主语从句的句子，谓语动词或系动词与表语的数一致。
What I want is a new bicycle. Which are your pictures?
3、两个以上的主语用and或both连接时，谓语用复数形式。例如：
Both Tom and Dick are good friends.
4、and所连接的两个词如指同一主体时，谓语则用单数形式。例如：
A singer and dancer was present at the party today.
A singer and a dancer were present at the party today.
5、集体名词作为整体意义时，谓语用单数形式，若指成员意义时，谓语则用复数形式。例如：
My family is a big one. My family are watching TV now.
6、主语是单数后面跟有as well as, with, together, like, but, except等短语时，谓语动词仍用单数形式。
(1)Kelly as well as the other students has learned how to type.
(2)Our school, with some few schools, was built in the 1960s.
7、两个主语由not only…but also, either…or, neither…nor相连接时，在肯定句中谓语变化取决于后者，在疑问句中取决于前者，例如：
Not only my parents but also my teacher has been to the party.
Either he or I am to go there.
Neither the students nor the teacher likes the film.
8、 people, police, cattle(牛群), militia(民兵)作主语时，谓语用复数形式。例如：
The police are still running after the murderer.
The cattle are grazing(放牧) in the fields.
9、 half of+单数名词时，谓语用单数形式;half of+复数名词时，谓语用复数形式。例如：
Half of the apple is rotten. Half of the apples are rotten.
10、书名、国名等名词作主语时，谓语用单数
Hamlet was written by Shakespear.
The United States is a large country.
11、each, either, neither等代词作主语时，谓语动词为单数;both做代词主语时，谓语用复数;none接不可数名词作主语时，谓语动词用单数，接可数名词复数时谓语单复均可。
12、the+形容词作主语时，谓语用复数形式。
The rich are not always happy though they have much money.
13、成对名词作主语时，谓语用单数形式，需要用冠词时只用一个，例如：
A knife and fork is on the table. Success and failure is common in life.
14、复合不定代词及many a+名词作主语时，谓语用单数形式。(表示复数意义)例如：
Everyone says it is a good film. Many a student likes it.
15、金钱、时间、重量、长度和距离等名词的复数形式作主语，谓语用单数变化。例如：
Five minutes is enough. 100 dollars seems to much for the coat.
16、who, which, thar引导定语从句作主语时，谓语变化取决于其代表的先行词的数，例如：
He is one of the students who were late this morning. All that glitters is not gold.
17、more than one+名词作主语时谓语用单数形式。例如：
More than one student was late today. More than one has learned about it.
18、分数或百分数后接单数名词作主语时，谓语用单数形式，接复数名词时，谓语用复数形式。例如：
About thirsty percent of my sister’s books are in English.
Two-thirds of the furniture in this room was bought last week.
80%(Four-fifths) of the students are boys.
19、“there be+并列主语“和”here be+并列主语“结构中的谓语形式一般应与并列主语中的第一个主语的数一致。
There is a pen and two books on the desk. There are some books and a pen on the desk.
