主语从句，即在复合句中充当主语成分的句子，例如"That he finished writing the composition in such a short time surprised us all"，他在很短的时间内写完作文让我们都很惊讶，此复合句主要描述的是某事让我们惊讶，某事就是该复合句的主语，因此“That he finished writing the composition in such a short time”便是该复合句的主语从句。
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引导主语从句的连词主要有： 0> m-J
从属代词：that whether "el}@
连接代词：who whoever whom whose what whatever which whichever ^l6q
连接副词：when where how why 969*mcq'
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主语从句例句图片 nmVL%66K
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中文名：主语从句 %uyRpG3,
外文名：Subject clause l =ZhHON
解释：合句中充当主语成分的句子 ] w(i,iJ
从属代词：that whether ~w' M8(
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定义 mh!;W=|/"
在复合句中充当主语成分的句子叫做主语从句。 1j<=TWit
第一部分 #m6 eG&a
常规主语从句，即句子在复合句中充当一个主语 d$/BF&n
主语从句是名词性从句，所以它的时态受主句的影响。 GM{m(Y
（1）That he finished writing the composition in such a short time surprised us all. 7^h?<X\
（2）Whether we will go for an outing tomorrow remains unknown. Kgi%Nd
（3）Who will be our monitor hasn't been decided yet. a 1Qg&s<
（4）Whom we must study for is a question of great importance. cejSGsW6q
（5）What caused the accident remains unknown. S,EXc^A7
（6）Whatever you did is right. ;$ =`BI)
（7）Who the watch belongs to is unknown. vDz)q
（8）What we need is time. >n)N=Zyu
（9）What we need are good doctors. RX%*:lXi_
名词性从句的时态规则： Iu^# +n
1）、主句谓语动词是现在或将来时，从句谓语动词可以用任何需要的时态。 ? r=cLC
I wonder what he is doing now. H?8KTl=e
Do you know when and where he was born?
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I'll write to tell him where I 'll meet him. IM}T2\tZ}
2）、主句谓语动词是过去时，从句谓语动词一般需用过去时。 8l0%:6XbI
（1）从句与主句的谓语动作同时发生，从句用一般过去时或过去进行时。 /Ws@YP
I thought that he studied hard. I2(5]85&]s
He told me his son was watching TV. wX"
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（2）从句谓语动作在主句谓语动作之后，从句用过去将来时。 5V4Ze;K
He said he would spend his holidays in Qingdao. 9~bje^M
（3）从句谓语动作在主句谓语动作之前，从句用过去完成时。 a; D{P`%n
They told me they had waited for me half an hour. /cUcfe#X
（4）从句如果有表示过去某一具体时间的状语，仍用过去时。 mdR:XuRD"t
She told me her brother died in 1945. 7^#f<m;Ar!
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3)客观的条件，从句时态不受丝毫影响。 .a1WwI
（1）从句说明的是不受时间限制的事实或真理（客观真理）。 <ZxxlJS)6
The teacher told us that the earth turns from west to east.
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He said Asia is the largest continent. ',?
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It was true that water freezes at thirty-two degrees Fahrenheit. ttuQ ,SD
（2）当从句表示的是反复出现的时态不变。 nV k o]y
She told me that she gets up at six o'clock every morning. T>e!DOW;
He asked me when the train usually starts. mS5'q q;t
（3）当从句是用来表达解释科技内容时时态不变。 kG/:fP
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（4）当从句的谓语动作仍在继续时，或者表示现在仍在的状态时，时态不变。 la>:%SD
He said that the workers in that factory are trying to fulfill the task in time. l9"0Wu@_x
She told me the other day that she is only 10. >
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（5）当从句的动作状态还未发生，要用一般式表示。强调与现在的联系。 3r!6Z5P7{'
He said he will wait for me this evening. }&Un8Rg"h
小结: bO>q`%&
（1）引导主语从句连词有that,whether,who,what,whatever等 a,tzt
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（2）连词位于句首不能省略 2%i_SX [
（3）主语从句大多数情况下视为第三人称单数，但也有例外，如例（9） t=o0
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注意：当what引导的名词性分句作主语时，主谓一致问题极为复杂。著名学者周海中教授在论文《关于what-分句作主语的主谓一致问题》中就这一问题做了深入研究，并给出了10种的主谓一致关系。这些一致关系值得英语学习者和使用者特别注意。 z %{ Z
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第二部分 16ahU$@-
为了防止句子头重脚轻，通常把形式主语it放在句首位置，真正主语搁置于句末 \B) a57
（1）It is certain that he will win the match. bD*V$w*P
（2）It is true that he has made a very important discovery in chemistry. JpqZVu"7
（3）It is very likely that they will hold a meeting. u :AKp<'
（4）It is strange that he should do that. Dn~r~aR$g
（5）It is important that we all should attend the meeting. k=1([x
（6）It is strange that the man should have stuck to his silly ideas. 9o5W\.A7[D
（7）It is a pity that we won't be able to go to the south to spend our summer vacation. P,U$
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（8）It is still a mystery what caused the accident. DKw%z8ft|
（9）It is said that he has gone to shanghai.(=He is said to have gone to shanghai) S` g:z b_
（10）It is known to all that the gun powder was first invented by the Chinese. &< hDl<E
（11）It is suggested that the work should be done with great care. s+IU%y/9$a
（12）It happened that the two cheats were there. (=The two cheats happened to be there) DT *'
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小结: w/_n$hX
（1）为避免头重脚轻，常以形式主语it引导从句。 It+形式主语谓语+从句。 Bu|U z0Y
（2）由于主语从句一般被认为是单数形式，形式主语的谓语动词、be动词+表语 均为单数第三人称形式或过去式. ,p2BB"^_i
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主语从句与宾语从句两者的用法和在句中的作用是不同的，下面从它们的各自用法来介绍。 -(*<2Hy4
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一．主语从句 >Y,3EI\
主语从句 定义：在句子中担当主语的是一个从句，这个从句就叫做主语从句。 #=@H-ZuD7
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。 hv "
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1. It 作形式主语和it引导强调句的比较 WH:[Y7D
①主语从句常用it作形式主语，一般常用句型为：It is+{名词/形容词/过去分词}+主语从句例如： ?naPti1GX
It is still a question whether she will come or not. IX/FKSuq
It is strange that you should like him. -
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It is still unknown which team will win the match. g;p]lVx=>
另外，还有一些比较多见的结构： 1X-K u GaD
It turned out that……; >)5=6{x
It has been proved that……; >y
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It happened/occurred that……; `D2wlyqO6
It is well-known that……等等 1-z*'Ghys
②而强调句则不同，它的结构是：It+be+被强调部分+that+从句 m3| KIUP
强调主语：It is the times that produce their heroes.时势造英雄 &uLxA w
强调宾语：It is English that Prof.Lin teaches us. wLa^pI4p ^
强调状语：It was in shanghai that I saw the film. >;E[XG^
判断是否是强调句有一个方法，就是将that以后的“句子的其余部分”拿出来单独看，看有没有缺成分，缺的是什么成分，再把谓语动词后面that前面的那部分，带到你认为缺成分的地方，如果放进去是一句完整的句子了，那就说明是强调句。 q; I` &JK
2. 用it 作形式主语的结构 i E DZ\\,
(1) It is +名词+that从句 R'E8>ee; ^
It is a fact that … 事实是…… 7 V/yU5
It is an honor that …非常荣幸 F~Kd5-I@
It is common knowledge that …是常识 to0tH^p D
(2) it is +形容词+that从句 `
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It is natural that… 很自然…… 4fDo
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It is strange that… 奇怪的是…… dhW; |
(3) it +不及物动词+that从句 Ru%:
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It seems that… 似乎…… JOj\#!\>k0
It happened that… 碰巧…… q.(p.uD
(4) it is+过去分词+that从句 T;- Zl[H
It is reported that… 据报道…… ?FRR";
It has been proved that… 已证实…… Q*TxjE7K
3.主语从句不可位于句首的五种情况 Df_W>QC
(1) if 引导的主语从句不可居于复合句句首。 qa 
