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什么是主语从句如何判断
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 necessary (important,natural,strange,etc.) that …
It is a pity (a shame,no wonder,etc.) that…
It is suggested (requested,proposed,desired,etc.) that…
主语从句连接词在从句中的成分
主语从句(SubjectClause) 定义:如果一个句子在复合句中充当一个主语,那么这个句子就是主语从句. 第一部分：常规主语从句，即句子在复合句中充当一个主语 （1）Thathefinishedwritingthecompositioninsuchashorttimesurprisedusall. （2）Whetherwewillgoforanoutingtomorrowremainsunknown. （3）Whowillbeourmonitorhasn'tbeendecidedyet. （4）Whomwemuststudyforisaquestionofgreatimportance. （5）Whatcausedtheaccidentremainsunknown. （6）Whateveryoudidisright. （7）Whosewatchwaslostisunknown. （8）Whatweneedistime. （9）Whatweneedaregooddoctors. 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）Itiscertainthathewillwinthematch. （2）Itistruethathehasmadeaveryimportantdiscoveryinchemistry. （3）Itisverylikelythattheywillholdameeting. （4）Itisstrangethatheshoulddothat. （5）Itisimportantthatweallshouldattendthemeeting. （6）Itisstrangethatthemanshouldhavestucktohissillyideas. （7）Itisapitythatwewon'tbeabletogotothesouthtospendoursummervacation. （8）Itisstillamysterywhatcausedtheaccident. （9）Itissaidthathehasgonetoshanghai.(=Heissaidtohavegonetoshanghai) （10）ItisknowntoallthatthegunpowderwasfirstinventedbytheChinese. （11）Itissuggestedthattheworkshouldbedonewithgreatcare. （12）Itseemsthathehasseenthefilm.(=Heseemstohaveseenthefilm) （13）Ithappenedthatthetwocheatswerethere.(=Thetwocheatshappenedtobethere) 小结: （1)以that引出的主语从句,常以形式主语it引导.Itis+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+havedone)例句4,5,6,11. 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，介绍：）~ 一．主语从句 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。 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： Itisapitythatyoudidn’tgotoseethefilm. 2.用it作形式主语的结构 (1)Itis＋名词＋从句 Itisafactthat…事实是… Itisanhonorthat…非常荣幸 Itiscommonknowledgethat…是常识 (2)itis＋形容词＋从句 Itisnaturalthat…很自然… Itisstrangethat…奇怪的是… (3)itis＋不及物动词＋从句 Itseemsthat…似乎… Ithappenedthat…碰巧… (4)it＋过去分词＋从句 Itisreportedthat…据报道… Ithasbeenprovedthat…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)Itissaid,(reported)…结构中的主语从句不可提前。例如： ItissaidthatPresidentJingowillvisitourschoolnextweek. (3)Ithappens…,Itoccurs…结构中的主语从句不可提前。例如： Itoccurredtohimthathefailedintheexamination. (4)Itdoesn’tmatterhow/whether…结构中的主语从句不可提前。例如： Itdoesn’tmatterwhetherheiswrongornot. (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： Isitlikelythatitwillrainintheevening? 4.What与that在引导主语从句时的区别 What引导主语从句时在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： Whatyousaidyesterdayisright. 二：宾语从句的几个特征：1、引导词：what\which\whose\when\whether\if\where 2语序：宾语从句必须是用陈述语句。 如：Ithinkthatyoumustworkharder. 宾语从句的引导词、连接词的区别、否定转移等现象。 (1)表达时间的几个句型：一般用when或者是whattime： Whattimewillthetrainleave? 由于时刻都是固定的，也可以用一般现在时代替一般将来时： Whattimedoesthetrainleave? (2)时间的表达方式：8：19(nineteenpasteight),7:57(threetoeight)，在时间的中间也可以加上分的单词(minutes) (3)hadbetter+动词原型。意思是提要求，建议。但是上下级不能用这种方式，因为语气太重： Youhadbettergiveupsmoking. (4)sbleavesth+地点 Ileftmybookinmyclassroomyesterday. (5)mayIhaveyourname(address\age)?一般询问对方的年龄、名字等，不要习惯以前的问法，这样很不礼貌，而是要采访上面的问法。以前的习惯是：howoldareyou?\what'syourname? (6)修饰名词的代词次序：限-描-大-形---年---颜----籍----物--------类+名词： thisisabridge. Thisisabeautifulbridge 补充：从句的语序永远是陈述句。
英语中的主语从句、定语从句、宾语从句以及表语从句的详细总结
1.主语从句 1）主语从句可直接位于主语的位置，如果从句较长，谓语又较短，可用it作形式主语，而将从句放在句末。常见的句型有： *It is a fact\a pity\a question\good news that... *It seems\appears\happened\has turned out that... *It is clear\important\likely\possible that... *It is said\reported\estimated\has been proved that... It is said that comic books create a connection between people of the same generation. It seems that the performance is very useful. 2)what引导的主语从句表示“...的东西时”，一般不用it作形式主语。 What we lack is experience. 3)what,who,when,why,whether等词含有各自的疑问意义，但它们引导的主语从句，都用陈述语序。 How the plan is to be carried out should be discussed again. I did know why I felt like crying. 2.宾语从句 1）宾语从句可位于及物动词、介词和某些形容词后。连词that常可省略。介词后一般接疑问词引导的宾语从句。in that(因为),except that(除了),but that(只是）已构成固定搭配，其他介词后一般不接that引导的宾语从句。 *I promised that I would change the situation. *All this is different from what American young people would say about friendship. *He is certain that watching so much television is not good for children. *This article is well-written except that it is a bit too long. 2)宾语从句后如有宾补，要用形式宾语it来代替，而把宾语从句移至宾补之后。 He has made it clear that he would not change his mind. 3)在think,believe,suppose,expect等动词后的宾语从句中，如果谓语是否定的，一般将否定词移至主句谓语上，宾语从句则变成肯定形式。 He didn't think that the money was well spent. 3.表语从句 表语从句出现在结构为“主语+系动词+表语从句”的句子中。表语从句除可用that,what,when,why,whether,how等引导外，还可由because,as if(though)等引导。that常可省略。如主句主语为reason,只能用that引导表语从句，不可用because. Perhaps the most important thing to remember is that there is no one common type of life in America. The reason why so many people died there is that there were not enough food supplies. It looks as if successful international cultural communication will make the world smaller. 4.同位语从句 同位语从句用于对前面出现的名词作进一步说明，一般用连词that引导，由于先行名词的意义不同，也可用whether,who,when,where,what,why,how等引导。常见的先行名词有fact,idea,belief,news,hope,conclusion,evidence,suggestion,order,problem,report,decision.有时由于谓语较短，将同位语从句位于谓语之后。 She finally made the decision that she would join the fashion show. I had no idea how many books I could borrow at a time. The news came that their team had won the championship. 5.定语从句 定语从句所修饰的先行词可以是名词或代词，也可以是一个句子。定语从句通常位于先行词之后，由关系代词或关系副词引导。 *限制性定语从句 限制性定语从句修饰先行词，对先行词起修饰作用，紧接先行词之后，无逗号，若省去，原句意思不完整。引导定语从句的关系代词有who,whom,whose,which,that等。who,whom,whose用于指人，whose有时也可指物，相当于of which；which用于指物；that既可指人也可指物，但只用于限制性定语从句中。关系代词除了引导定语从句，替代先行词外，还在从句中担任主语、宾语、定语等。 The computers and cables which make up the Internet are owned by people and organizations. Those who live alone or who are sick may have trouble in getting close to other people. The girl whose parents died in an accident is living with her grandmother. 1)当先行词是all,anything,everything,something,nothing等不定代词或先行词前有first,last,any,few,much,some,no,only以及形容词最高级修饰时，只能用关系代词that引导从句。 That is all that I've heard from him. He's the first person that I'm going to interview this afternoon. 2)关系代词的省略 在从句中作宾语的关系代词常可省略。关系代词紧跟介词，作介词宾语时不可用that，只可用which或whom引导从句，并且不可省略，但当介词位于宾语从句句末时，作为介词宾语的关系代词仍可用that，也可省略。 This is one of those things with which we have to put up. This is one of those things (which\that) we have to put up with. 3)引导定语从句的关系副词有when,where,why等。关系副词在从句中作状语，意义上相当于一个“介词+which”的结构。 Even in comic books where(=in which) there are no words,the stories are fully expressed through the drawings. No one knows the reason why(=for which) he was so angry that day.*非限制性定语从句 非限制性定语从句既可修饰先行词，也可修饰整个主句，起补充说明作用，与主句之间有逗号隔开，若省去，原句意思不受影响。不可用that引导非限制性定语从句。关系词不可省略。 Every object has a gravitational pull,which is rather like magnetism. *“介词+which\whom\whose”引导的定语从句 “介词+which\whom\whose”可引导限制性定语从句，也可引导非限制性定语从句，该结构中介词的选择取决于从句谓语动词的固定搭配，或先行词的习惯搭配。 This is the computer on which he spent all his savings It is written by a person with whom we are all familiar. *as引导的定语从句 as引导的定语从句主要用于“such...as”及“the same...as”的结构中，代替先行词是人或物的名词。as引导非限制性定语从句时，代替整个主句，从句可位于主句之前、之后或中间。 These are not such problems as can be easily solved.(as代替先行词problems) As is mentioned above,no single company or group can control what happens on the Internet.(as代替主语) 6.状语从句 *时间状语从句 引导时间状语从句的从属连词和词组有： 1）when,whenever,while,as,after,before,since,till,until,once等。 We have learnt quite a lot about it since we came here. 2)as soon as,hardly(scarcely)...when,no sooner...than,each(every) time,the moment,immediately(that)等。 As soon as I sent an e-mail message,I received positive responses. The moment he heard the good news,he jumped with joy. *地点状语从句 引导地点状语从句的连词是where,wherever. Wherever she went,she took her little daughter with her. *原因、结果和目的状语从句 1）引导原因状语从句的从属连词有：because,as,since,now(that),seeing that,considering that,in that等。 Considering that he is a freshman,we must say he is doing well. 2)引导结果状语从句的连词有：so...that,such...that,so that,that,so等。 Mickey Mouse is so attractive that the children are reluctant to leave. 3)引导目的状语从句的连词有：so that,in order that,for fear that,lest等，从句常使用may,might,can,could,would等情态动词。 We got up early this morning so that we could catch the first bus to the railway station. *条件和让步状语从句 1）引导条件状语从句的连词和词组有if,unless,as(so) long as,on condition that,in case,provided(providing) that,supposing等。 As long as you have the right equipment,you can use a telephone line to transmit computer data. 2)引导让步状语从句的连词和词组有though,although,whether,even though,even if,no matter what(when,how...),whatever(whenever,wherever,however....)等。though,even if等引导状语从句可转换成含有as的部分倒装结构，具有强调意义。其结构为“形容词（副词、动词、名词）+as+主语+谓语”。 No matter what you may say,I would not change my mind. Young as he is,he is quite experienced in this work.(=though he is young) Child as he is,he can speak English fluently.(=though he is a child) *方式状语从句 引导方式状语从句的连词有as,just as,as if,as though等。as if,as though引导的状语从句中，谓语动词常用虚拟语气，表示与事实相反。 The young man made the experiment just as the teacher had taught him. Everything went on as usual as if nothing had happened.
主语从句的句式分为哪几种类型
1、由连词that引导的主语从句。
例如：That you will win the medal seems unlikely.
你想获得奖牌看起来是不可能的。
That you are so indifferent bothers me.
你如此冷淡使我很烦恼。
That she survived the accident is a miracle.
她在事故中幸免于难简直是奇迹。
2、用连接代词或连接副词if, whether 引导的主语从句。
例如： Which of them escaped from the prison is still a mystery.
他们哪一个是从监狱里逃跑的，仍然是个谜。
When they will come hasn’t been made pubic.
他们什么时候来还不知道。
Whether she is coming or not doesn’t matter too much.
她来不来都无关紧要。
3、用关系代词引导的主语从句。
例如：What you need is more practice.
你所需要的是更多的训练。
What I want to know is this. 我想知道的就是这事。
Whatever we do is to serve the people.
我们无论做什么都是为人民服务。
4、主语从句可以直接放在主语位置上，也可以用it作形式主语，而将从句放在句末（尤其是当谓语较短时）。
例如：That light travels in straight lines is known to all.
扩展资料
主语从句，即在复杂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。
引导主语从句的连词主要有：
从属连词：that whether
连接代词：who whoever whom whose what whatever which whichever
连接副词：when where how why
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第三人称单数，但也有例外，如例（9）
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。
参考资料：百度百科——主语从句
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