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精选优质文档-倾情为你奉上主语从句讲解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任主语的从句，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.引导主语从句的关联词有三类：(1)从属连词that，whetherThat they were true sisters was clear from the facial resemblance between them.Whether hell come here isnt clear.(2)连接代词who, whom, whose, what, which, whoever, whatever, whichever，What she did is not yet known.How this happened is not clear to anyone.Whoever comes is welcome.(3)连接副词where，when, how, why2.主语从句是在复合句中充任主语的从句，其功同名词一样。为了避免头重脚轻，常用it作形式主语,而把真正主语放在句子末尾。How the book will sell depends on its author.That he is the best student in the class is obvious.= It is obvious that he is the best student in the class.注意：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 doesnt matter how/whether 结构中的主语从句不可提前。例如：It doesnt 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?3.主语从句用陈述语序。关联词位于句首不能省略。How he became a great scientist is known to us all.That he finished writing the composition in such a short time surprised us all.4.主语从句中注意的事项：1）在主语从句中，谓语动词大凡用单数。Whatever he says is of no importance.Whoever says this is wrong.但谓语动词用单数还是复数，不可一概而论，而要视句子的意义而定What I need is money.What I need are books.2）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任句子成分，如主语、宾语、表语，而that则不然。What you said yesterday is right.That she is still alive is a consolation.3）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，主要是为了平均句子结构，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。1. It作形式主语和it引导强调句的比较主语从句常用it作形式主语，大凡常用句型为：It is+名词/形容词/过去分词+主语从句例如：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.而强调句则例外，它的结构是：It+be+被强调部分+that+从句强调主语：It is the times that produce their heroes.时势造英雄强调宾语：It is English that Prof.Lin teaches us.强调状语：It was in shanghai that I saw the film.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，如果放进去是一句统统的句子了，那就说明是强调句。It is still a mystery what caused the accident.It is a mystery that his death remained.4) whether与ifwhether引导主语从句时,常置于句首(此时whether不能用if代替),也有后移的用法(此时whether可以用if代替)Whether they will come is not yet known.It is not yet known whether / if they will go there.whether和if的区别还有：1.引导表语从句用whetherThe question is whether you should accept it.2. whether可以引导从句作介词的宾语Im not interested in whether theyll go or not.It depends on whether we have got enough money.3. whether可以直接跟动词不定式连用I didnt know whether to laugh or to cry.She hasnt decided whether to go or not.5）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 is不及物动词从句It seems that似乎 It happened that碰巧It appears that似乎(4) It过去分词从句It is reported that据报道 It has been proved that已证实It is said that据说专心-专注-专业
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