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高中英语语法之名词性从句之主语从句

在句子中起名词作用的句子叫名词性从句(Noun Clauses）。名词性从句的功能相当于名词词组, 它在复合句中能担任主语、宾语、表语、同位语、介词宾语等，因此根据它在句中不同的语法功能，名词性从句又可分别称为主语从句、宾语从句、表语从句和同位语从句。

一、引导名词性从句的连接词

引导名词性从句的连接词可分为三类：

连词：that（无任何词意）whether,if（均表示“是否”表明从句内容的不确定性）as if ,as though（均表示“好像”，“似乎”）以上在从句中均不充当任何成分

连接代词：what, whatever, who, whoever, whom,whose, whichever,whomever 连接副词：when, where, how, why,how many,how much,how often 不可省略的连词： 1.介词后的连词

2.引导主语从句和同位语从句的连词不可省略。

That she was chosen made us very happy.We heard the news that our team had won.比较：whether与if 均为“是否”的意思。但在下列情况下，只可用whether：

1.whether引导主语从句并在句首2.引导表语从句 3.whether从句作介词宾语4.从句后有“or not” Whether he will come is not clear.大部分连接词引导的主语从句都可以置于句末，用 it充当形式主语。

It is not important who will go.It is still unknown which team will win the match.二.主语从句

1、作句子主语的从句叫主语从句。主语从句通常由从属连词that，whether，if和连接代词what，who，which，whatever，whoever以及连接副词how，when，where，why等词引导。that在句中无词义，只起连接作用；连接代词和连接副词在句中既保留自己的疑问含义、又起连接作用，在从句中充当从句的成分。例如：

What he wants to tell us is not clear.他要跟我们说什么，还不清楚。Who will win the match is still unknown.谁能赢得这场比赛还不得而知。

It is known to us how he became a writer.我们都知道他是如何成为一名作家的。

Where the English evening will be held has not yet been announced.英语晚会将在哪里举行，还没有宣布。有时为避免句子头重脚轻，常用形式主语it代替主语从句作形式主语放于句首，而把主语从句置于句末。主语从句后的谓语动词一般用单数形式。常用句型如下：

（1）It + be + 名词 + that从句（2）It + be + 形容词 + that从句（3）It + be + 动词的过去分词 + that从句（4）It + 不及物动词 + that 从句

另注意在主语从句中用来表示惊奇、不相信、惋惜、理应如此等语气时，谓语动词要用虚拟语气“(should)+do”，常用的句型有：It is neceary(important, natural, strange, etc.)that …

It is suggested(requested, proposed, desired, etc.)that…

2、第一部分：常规主语从句，即句子在复合句中充当一个主语 主语从句的时态：不受主句的时态影响和限制。

（1）That he finished writing the composition in such a short time surprised us all.（2）Whether we will go for an outing tomorrow remains unknown.（3）Who will be our monitor hasn't been decided yet.（4）Whom we must study for is a question of great importance.（5）What caused the accident remains unknown.（6）Whatever you did is right.（7）Who the watch belongs to was lost is unknown.（8）What we need is time.（9）What we need are good doctors.小结:（1)引导主语从句连词有that,whether,who,what,whatever等（2)连词位于句首不能省略（3)主语从句大多数情况下视为三单,但也有例外,如例9

第二部分：为了防止句子头重脚轻，通常把形式主语it放在主语位置，真正主语搁置于句末（1）It is certain that he will win the match.（2）It is true that he has made a very important discovery in chemistry.（3）It is very likely that they will hold a meeting.（4）It is strange that he should do that.（5）It is important that we all should attend the meeting.（6）It is strange that the man should have stuck to his silly ideas.（7）It is a pity that we won't be able to go to the south to spend our summer vacation.（8）It is still a mystery what caused the accident.（9）It is said that he has gone to shanghai.(=He is said to have gone to shanghai)（10）It is known to all that the gun powder was first invented by the Chinese.（11）It is suggested that the work should be done with great care.（12）It seems that he has seen the film.(=He seems to have seen the film)（13）It happened that the two cheats were there.(=The two cheats happened to be there)小结:（1)以that 引出的主语从句,常以形式主语it引导.It is +形容词/名词/某些动词ed + that 从句.（2)在有些that从句中要用虚拟语气(should+do/should+have done)例句4,5,6,11.3、主语从句的用法

主语从句是在复合句中充当主语的从句，通常放在主句谓语动词之前或由形式主语it代替，而本身放在句子末尾。

1.It 作形式主语和it引导强调句的比较

It 作形式主语代替主语从句，主要是为了平衡句子结构，主语从句的连接词没有变化。而it引导的强调句则是对句子某一部分进行强调，无论强调的是什么成分，都可用连词that。被强调部分指人是也可用who/whom。例如： It is a pity that you didn’t go to see the film.2.用it 作形式主语的结构

(1)It is ＋名词＋从句

It is a fact that … 事实是…

It is an honor that …非常荣幸

It is common knowledge that …是常识

(2)it is ＋形容词＋从句

It is natural that… 很自然…

It is strange that… 奇怪的是…

(3)it ＋不及物动词＋从句

It seems that… 似乎…

It happened that… 碰巧…

(4)it is＋过去分词＋从句

It is reported that… 据报道…

It has been proved that… 已证实… 3.主语从句不可位于句首的五种情况

(1)if 引导的主语从句不可居于复合句句首。

(2)It is said ,(reported)…结构中的主语从句不可提前。例如：

It is said that President Jingo will visit our school next week.(3)It happens…, It occurs… 结构中的主语从句不可提前。例如：

It occurred to him that he failed in the examination.(4)It doesn’t matter how/whether …结构中的主语从句不可提前。例如：

It doesn’t matter whether he is wrong or not.(5)含主语从句的复合句是疑问句时，主语从句不可提前。例如：

Is it likely that it will rain in the evening?

4.What 与that 在引导主语从句时的区别

What 引导主语从句时在从句中充当句子成分，如主语．宾语．表语，而that 则不然。例如： What you said yesterday is right.1.________ makes mistakes must correct them.A.What B.That C.Whoever D.Whatever 2.It worried her a bit ____ her hair was turning grey.A.while B.that C.if D.for 3.When and why he came here ________ yet.A.is not known B.are not known C.has not known D.have not known 4.________ is no reason for dismiing her.A.Because she was a few minutes late B.Owing to a few minutes late C.The fact that she was a few minutes late D.Being a few minutes late 5.________ Tom liked to eat was different from ________.A.That…that you had expected B.What …that you had expected C.That…what you had expected D.What…what you had expected

6.________ we go swimming every day ________ us a lot of good.A.If...do B.That...do C.If...does D.That...does 7.It ________ Bob drives badly.A.thinks that B.is thought what C.thought that D.is thought that 8.It's uncertain ________ the experiment is worth doing.A.if B.that C.whether D.how 9.________ the boy didn't take medicine made his mother angry.A.That B.What C.How D.Which 10.____ we can't get seems better than ____ we have.A.What, what B.What, that C.That, that D.That, what 11.____ you don't like him is none of my busine.A.What B.Who C.That D.Whether 12..____ we'll go camping tomorrow depends on the weather.A.If B.Whether C.That D.Where 13._________is going to do the job will be decided by the Party committee.A.That B.Why C.How D.Who 14._______we'll finish translating the book depends on the time.A.When B.Why C.What D.That 15.______he won't go there is clear to all of us.A.How B.What C.Why D.This 16.______the house will be built will be discued at tomorrow's meeting.A.If B.Where C.That D.What 17.._______you come or not is up to you.A.What B.If C.Why D.Whether 18.._______makes mistakes must correct them.A.Who B.Anyone C.Whoever D.Anybody 19.._______team will win the match is a matter of public concern.A.Which B.That C.If D.How 20..________leaves the room last ought to turn off the lights.A.Anyone B.The person C.Whoever D.Who

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