在復(fù)合句中充當(dāng)主語成分的句子叫做主語從句。

一.

引導(dǎo)主語從句連詞有that,

who,what,whatever等 定義:如果一個句子在復(fù)合句中充當(dāng)一個主語,那么這個句子就是主語從句. 第一部分：常規(guī)主語從句，即句子在復(fù)合句中充當(dāng)一個主語 

（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 has'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）Whose watch was lost is unknown. 

（8）What we need is time. 

（9）What we need are good doctors. 

小結(jié): （1)引導(dǎo)主語從句連詞有that,whether,who,what,whatever等 （2)連詞位于句首不能省略 （3)主語從句大多數(shù)情況下視為單三,但也有例外,如例9 第二部分：為了防止句子頭重腳輕，通常把形式主語it放在主語位置，真正主語擱置于句末 

（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) 

小結(jié): （1)以that 引出的主語從句,常以形式主語it引導(dǎo).  It is +形容詞/名詞/某些動詞ed + that 從句. （2) 在有些that從句中要用虛擬語氣  (should+do/should+have done)  

二、主語從句與形式主語it

有時為了考慮句子平衡，通常在主語從句處使用形式主語it，而將真正的主語從句移至句末。這分三種情況：

(1) 對于以連詞that引導(dǎo)的主語從句，通常用形式主語代主語從句：

It’s a pity that he didn’t come. 很遺憾他沒來。

It is important that he should know about this. 他必須知道此事。

It’s vital that we bepresent. 我們出席是至關(guān)重要的。

Itwasintendedthatyoubethecandidate. 大家的意圖是讓你當(dāng)候選人。

Itisimportantthatthismissionnotfail. 這項使命不失敗至關(guān)重要。

Itisessentialthatameetingbeconvenedthisweek. 本周開一次會非常重要。

Itisappropriatethatthistaxbeabolished. 廢除這個稅是恰當(dāng)?shù)摹?/p>

It’sunfairthatsomanypeopleshouldlosetheirjobs. 竟有這么多人失業(yè)這是不公平的。

It’samazingthatsheshouldhavesaidnothingaboutit. 她竟未談及此事令人驚訝。

It’sunthinkablethattheyshoulddenymyrequest. 他們竟然拒絕我的請求，這是不可思議的。

Thattheyshouldrefusetosignthepetitionrequiredgreatcourage. 他們拒絕在請愿書上簽字這是需要很大勇氣的。

(2) 對于以連接代詞(副詞)引導(dǎo)的主語從句，可以使用形式主語代主語從句，也可直接在句首使用主語從句：

Whethertheywouldsupportuswasaproblem. 他們是否會支持我們還是一個問題。

Itwasaproblemwhethertheywouldsupportus. 他們是否會支持我們還是一個問題。

Itremainstobeseenwhetheritwilldousharmorgood. 它對我們是利是害，還得看看再說。

(3) 對關(guān)系代詞型what引導(dǎo)的主語從句，通常直接將主語從句放在句首。如：

Whatweneedismoney. 我們需要的是錢。

WhatIwanttoknowisthis. 我想知道的就是這一點(diǎn)。

有時也可將助用形式主語。如：

Itisclearenoughwhathemeant. 他是什么意思很清楚。

(4) 如果句子是疑問句，則必須用帶形式主語it的結(jié)構(gòu)：

Isittruethatheisthegirl’sfather? 他是那女孩的父親，是真的嗎？

Howisitthatyouarelateagain? 你怎么又遲到了？

that

引導(dǎo)主語從句的連詞that 有時可省，有時不能省，其原則是：若that引導(dǎo)的主語從句直接位于句首，則that不能省略；若that引導(dǎo)的主語從句位于句末，而在句首使用了形式主語it，則that可以省略：

Thatyoudidn’tgotothetalkwasapity. 很遺憾你沒去聽報告。(that不可省)

Itwasapity (that) youdidn’tgotothetalk. 很遺憾你沒去聽報告。(that可省)

常規(guī)主語從句，即句子在復(fù)合句中充當(dāng)一個主語

主語從句的時態(tài)：不受主句的時態(tài)影響和限制。

（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 is unknown.

（8）What we need is time.

（9）What we need are good doctors.

小結(jié)

（1）引導(dǎo)主語從句連詞有that,whether,who,what,whatever等

（2）連詞位于句首不能省略

（3）主語從句大多數(shù)情況下視為第三人稱單數(shù)，但也有例外，如例（9）

為了防止句子頭重腳輕，通常把形式主語it放在句首位置，真正主語擱置于句末

（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 happened that the two cheats were there. (=The two cheats happened to be there)

小結(jié):

（1）為避免頭重腳輕，常以形式主語it引導(dǎo)從句。 It+形式主語謂語+從句。

（2）由于主語從句一般被認(rèn)為是單數(shù)形式，形式主語的謂語動詞、be動詞+表語 均為單數(shù)第三人稱形式或過去式.

注意：當(dāng)what引導(dǎo)的名詞性分句作主語時，主謂一致問題極為復(fù)雜。著名學(xué)者周海中教授在論文《關(guān)于what-分句作主語的主謂一致問題》中就這一問題做了深入研究，并給出了10種的主謂一致關(guān)系。這些一致關(guān)系值得英語學(xué)習(xí)者和使用者特別注意。

主語從句的用法

主語從句與賓語從句兩者的用法和在句中的作用是不同的，下面從它們的各自用法來介紹。

一．主語從句

主語從句 定義：在句子中擔(dān)當(dāng)主語的是一個從句，這個從句就叫做主語從句。

主語從句是在復(fù)合句中充當(dāng)主語的從句，通常放在主句謂語動詞之前或由形式主語it代替，而本身放在句子末尾。

1. It 作形式主語和it引導(dǎo)強(qiáng)調(diào)句的比較

①主語從句常用it作形式主語，一般常用句型為：It is+{名詞/形容詞/過去分詞}+主語從句例如：

It is still a question whether she will come or not.

It is strange that you should like him.

It is still unknown which team will win the match.

另外，還有一些比較多見的結(jié)構(gòu)：

It turned out that……;

It has been proved that……;

It happened/occurred that……;

It is well-known that……等等

②而強(qiáng)調(diào)句則不同，它的結(jié)構(gòu)是：It+be+被強(qiáng)調(diào)部分+that+從句

強(qiáng)調(diào)主語：It is the times that produce their heroes.時勢造英雄

強(qiáng)調(diào)賓語：It is English that Prof.Lin teaches us.

強(qiáng)調(diào)狀語：It was in shanghai that I saw the film.

判斷是否是強(qiáng)調(diào)句有一個方法，就是將that以后的“句子的其余部分”拿出來單獨(dú)看，看有沒有缺成分，缺的是什么成分，再把謂語動詞后面that前面的那部分，帶到你認(rèn)為缺成分的地方，如果放進(jìn)去是一句完整的句子了，那就說明是強(qiáng)調(diào)句。

2. 用it 作形式主語的結(jié)構(gòu)

(1) It is +名詞+that從句

It is a fact that … 事實是……

It is an honor that …非常榮幸

It is common knowledge that …是常識

(2) it is +形容詞+that從句

It is natural that… 很自然……

It is strange that… 奇怪的是……

(3) it +不及物動詞+that從句

It seems that… 似乎……

It happened that… 碰巧……

(4) it is+過去分詞+that從句

It is reported that… 據(jù)報道……

It has been proved that… 已證實……

3.主語從句不可位于句首的五種情況

(1) if 引導(dǎo)的主語從句不可居于復(fù)合句句首。

(2) It is said , (reported) …結(jié)構(gòu)中的主語從句不可提前。例如：

It is said that President Jingo will visit our school next week.

(3) It happens…, It occurs… 結(jié)構(gòu)中的主語從句不可提前。例如：

It occurred to him that he failed in the examination.

(4) It doesn’t matter how/whether …結(jié)構(gòu)中的主語從句不可提前。例如：

It doesn’t matter whether he is wrong or not.

(5) 含主語從句的復(fù)合句是疑問句時，主語從句不可提前。例如：

Is it likely that it will rain in the evening?

4. What 與that 在引導(dǎo)主語從句時的區(qū)別

What 引導(dǎo)主語從句時在從句中充當(dāng)句子成分，如主語．賓語．表語，而that 則不然。例如：

What you said yesterday is right.

二：賓語從句用以區(qū)分主語從句的幾個特征：

1、引導(dǎo)詞：what\which\whose\when\whether\if\where

2語序：賓語從句必須是用陳述語句。

如：I think that you must work harder.

賓語從句的引導(dǎo)詞、連接詞的區(qū)別、否定轉(zhuǎn)移等現(xiàn)象。

(1)表達(dá)時間的幾個句型：一般用when或者是what time：

What time will the train leave?

由于時刻都是固定的，也可以用一般現(xiàn)在時代替一般將來時：

What time does the train leave?

(2)時間的表達(dá)方式：8：19(nineteen past eight),7:57(three to eight)，在時間的中間也可以加上分的單詞(minutes)

(3)had better +動詞原型。意思是提要求，建議。但是上下級不能用這種方式，因為語氣太重：

You had better give up smoking .

(4)sb leave sth +地點(diǎn)

I left my book in my classroom yesterday.

(5)may I have your name(address\age)?一般詢問對方的年齡、名字等，不要習(xí)慣以前的問法，這樣很不禮貌，而是要采訪上面的問法。以前的習(xí)慣是：how old are you? \what's your name?

(6)修飾名詞的代詞次序：限-描-大-形---年---顏----籍----物--------類+名詞：

this is a bridge.

This is a beautiful bridge

補(bǔ)充：從句的語序永遠(yuǎn)是陳述句。[1]