哪些从句作主语时可用it作形式主语.doc

哪些从句作主语时可用it作形式主语原则上说，it用作形式主语可以代替下列从句：1. that从句It is quite clear that he has read the book. 很显然，他读过这本书。(HM)2. what从句It doesnt matter what he says. 他说什么没关系。(HM)It was clear enough what he meant. 他的意思是很明显的。3. who从句It hasnt been decided who will be sent to work there. 还没决定将派谁到那里工作。4. how从句It struck her how gentle he was being. 她深深感到他多么温存。5. when从句It hasnt been made clear when the conference is to take place. 会议什么时候召开还没有宣布。6. where从句Its not known where she went. 她到哪里去了没人知道。It did not matter much where he lived. 他在哪里住都没有关系。7. why从句It was clear why he had asked for a conference. 他为什么要求召开会议原因很清楚。8. whether从句It makes little difference whetherwe go or stay. 我们去还是留没有多大差别。Its not yet settled whether I am going to America. 我去不去美国还没定。it用作形式主语代替动名词主要用于哪些句式it用作形式主语代替动名词的用法主要见于以下句式： 1. It is no use (no good, fun, great fun, a new experience, a great honour, etc) doing sth。如：It is no good talking. 空谈是没有用的。Its fun working for him. 为他工作很有意思。Its great fun sailing a boat. 扬帆驾舟十分有趣。Its no use shouting at himhes deaf. 向他叫喊是没有用的他耳聋。It has been a great honour your coming to visit us. 你来看望我们是极大荣幸。2. It is good (nice, useless, interesting, pleasant, tiring, etc) doing sth。如：It is useless speaking. 光说没有用。It was pleasant sitting there. 坐在那里很愉快。Its so nice sitting here with you. 和你坐在一起真是愉快。Its good hearing English spoken. 听到人讲英语，我很高兴。Its terribly tiring working late like this. 这样干到深夜是非常累人的。3. it is worth while doing sth。如：Its worth while doing the work. 这项工作值得做。Do you think its worth while quarrelling with me? 你认为和我吵值得吗? 4. 其他句式。如：It doesnt matterwasting a little money. 浪费一点钱没有关系。It felt funny being dressed like a peasant girl. 打扮成村姑感到有点怪怪的。Whats it like being married? 结婚是什么味道。如何区别引导名词从句的whether与thatwhether与that均可引导名词从句，该如何区别呢？_ well go camping tomorrow depends on the weather. A. If B. WhetherC. ThatD. When此题应选 B。容易误选A，C。1. 关于if与whether：两者都可引导宾语从句，常可换用; 但若引导主语从句，则用whether (不用if)，排除A。又如。如：他是否会来还是个问题。误：If he will come is a question. 正：Whether he will come is a question. 2. 关于whether和that：两者都可引导主语从句，其区别主要应从句意来考虑：whether表示“是否”，由它引导的主语从句的意思通常是不确定的；that 引导主语从句时，本身没有词义(that在其他名词性从句中也没有词义)，但是由that引导的整个主语从句的意思通常是确定的。试比较()：1. a. That well hold a meeting is decided. 我们要召开一次会议，这已决定了。b. Whether well hold a meeting is not decided. 我们是否要开一个会，这还没有决定。2. a. That he has left here is clear. 他已离开了这儿，这点很清楚。b. Whether he has left here is not clear. 他是 否已离开这儿，这还不清楚。3. a. That he can finish it in two hours is clear. 他能在两小时内完成它，这是显然的。b. Whether he can finish it in two hours is a question. 他能否在两小时内完成它还是问题。that与whether (if)引导名词性从句的区别两者均可引导宾语从句，也可引导语从句和表语从句(if 通常不行)，但两者含义不同，whether (if) 表示“是否”，that 却不表示任何含义。在它们所引出的从句中，that 表示一种肯定、明确的概念，而 whether (if) 则表示一种不肯定、不明确的概念。比较：Whether hell come is not known yet. 他是否来还不清楚。That hell come is known to us all. 我们都知道他会来。类似地，动词doubt (怀疑)后接宾语从句时，由于 doubt的含义不确定，故通常用 whether (if) 来引导其宾语从句，但若 doubt为否定式，则其后的宾语从句用 that 来引导。如：I doubt if you are honest. 我怀疑你是否诚实。I dont doubt that you are honest. 我不怀疑你是诚实的。如何理解引导名词性从句的what应如何理解引导名词性从句的what呢？它还是表示“什么”吗？请看题：_ he said at the meeting astonished everyone present. A. WhatB. ThatC. IfD. Whether分析：此题应选 A。选项 C(if) 显然不能选，因为 if 通常不能引导主语从句；选项 B(that) 和 D(whether) 虽然都可以引导主语从句，但两者除了意思不合题意外，还有它们在主语从句中都不充当句子成分，而此句中的 he said 缺宾语。在名词性从句中，what 根据情况不同，可能有两方面的用法和意思：1. 用作连接代词，表示“什么”(由疑问词变来)。如：I dont knowwhat he gave her. 我不知道他给了她什么。What he will say at the meeting is not known to us. 他在会上将说些什么，我们还不知道。2. 表示“所的(东西)”，在结构上相当于一个名词加一个定语从句(所以有人称这样用的what 为关系代词型的what)。如：把你买的东西拿给我看。Show me what you bought. Show me the thing that you bought. 这是他想要的东西。This is what he wants. This is the thing that he wants. 我们需要的是钱。What we need is money.() The thing that we need is money. 引导宾语从句that的省略问题名词从句作动词宾语时，前面的that常被省略，特别是在非正式语体中：I suggested (that) they should drive along the coast. 我建议他们沿着海岸开车。I hoped (that) I would / should succeed. 我曾希望我会成功。I know (that) he will be in time. 我知道他会赶得上的。He thinks (that) they will give him a visa. 他想他们会给他签证。I expect (that) the plane will he diverted. 我料想飞机会改变航线。在某些动词 (如answer, imply) 之后则一般需要用that。如：。She answered that she preferred to eat alone. 她回答说她愿意独自吃。I dont wish to imply that you are wrong. 我无意暗示你错了。The newspapers have implied tha