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1、Unit4主语从句 主语从句可以按其引导词的不同分为三类：第一类，用从属连词that引导的主语从句，例如： That we shall be late is certain. That the driver could not control his car was obvious. 这种结构主要是对that从句的内容进行强调，属正式文体，连词that不可以省略；但是在一般情况下，往往使用先行it结构，即用it作形式主语，而把that从句放到后面，这时，在口语中，连词that有时则可以省略。所以上述两句可以改为It is certain that we shall be late. It wa
2、s obvious that the driver could not control his car. 如果整个句子是疑问形式，就只能用先行it结构，例如Is it true that he would take the risk? Is it possible that they will come tomorrow？常使用先行it结构，用that从句作主语的句子有下列几个句型1、It + be + 形容词+that从句： It is clear that he was telling the truth. Its probable that well be a little late.
3、2It + be + 名词词组+ that从句： Its a pity that you cant go with us. 3It + 及物动词+宾语+ that： It worried her a bit that her hair was turning grey. It shocked me that Peter didnt tell anybody where he was. 4It + be +过去分词+ that+从句： It is said that he has been there many times. 5It +seem/happen/appearIt +等不及物动词等+
4、 that从句： It seems that he has lost something.注意:在上述第1和第2两种句型中，that从句前置与使用先行it，that从句后置在意义上没有什么差异；但使用先行it结构较为常见。在第3种句型中，that从句前置在语法上是可能的，但实际上并不常见，通常总是使用先行it结构 . 第4种句型实质上是被动结构，由于that从句不可以位于句首作被动句的主语，所以只能使用先行it结构。第5种句型已经形成了固定的搭配关系，that从句不能前置，只能使用先行it结构，不过，这种结构可以转换为带有不定式的简单句，例如： It happened that I had n
5、o money with me that day. I happened to have no money with me that day. 第二类，用连接代词who、whose、which、what，连接副词when、where、how、why，以及连词whether（或if）引导的主语从句，例如Who was responsible for the accident is not yet clear. It is not yet clear who was responsible for the accident. What he did is not yet known. It is
6、not yet known what he did. Whether it is true remains a problem.It remains a problem whether / if it is true.从以上例句可以看出，这类主语从句可以直接放在句首作主语，也可以使用先行it结构，把主语从句放在后面，两种结构可以互换，意义上无差异，但用if 引导主语从句时，只能采取先行it结构，也就是说if不可以引导置于句首的主语从句.第三类，用what、whatever、where、wherever、whoever、whichever等代词引导的主语从句，例如; What he said a
7、t the meeting encouraged everyone. Whoever fails to see this will make a big blunder.这类从句一般相当于带有定语从句所修饰的名词词组，即在结构上相当于一个名词加上一个定语从句，例如： What he wants to buy is a ten-speed bicycle. The thing that he wants to buy is a ten-speed bicycle. Whoever breaks the law is sure to be punished. Anyone who breaks t
8、he law is sure to be punished.切记，这类主语从句不可以使用先行it结构。 上述第二类主语从句与第三类主语从句尽管在形式上十分相似，但实际上是不同的。第二类结构中用连接代/副词引导的从句系由特殊疑问句转化而来，以whether/if引导的从句系由一般疑问句转化而来，自然含有疑问的意味，例如： When they will have the sports meet is still a question. When will they have the sports meet?Who he is doesnt concern me. Who is he？ Whethe
9、r he will join us wont make too much difference. Will he join us？而第三类结构中的主语从句则没有疑问的意味。试比较下列各句 What caused the accident is a complete mystery. What caused the accident was a broken bottle. What she looks like doesnt matter. What shed like is a digital watch.上述各句中尽管都有一个以what引导的主语从句，但其意义不尽相同；第和句中的主语从句系
10、由“What caused the accident？”和“What does she look like？”转化而来，所以可以改成： It is a complete mystery what caused the accident. It doesnt matter what she looks like.第句中的主语从句含义分别为“The thing that caused the accident”和“The thing which shed like”，所以不含疑问意味，因此不可以说： It was a broken bottle what caused the accident.
11、It is a digital watch what shed like.但是可以说： It was a broken bottle that caused the accident. It is a digital watch that shed like.不过，这已不是主语从句，而是强调结构了。名词性从句通常以“引导词正常陈述句语序”的基本形式出现，有时会省略引导词，例如： Where the meeting is to be held has not been decided. 在哪里开会还没决定。(引导词where 在正常陈述句语序的主语从句中作地点状语) Whether he wil
12、l attend the party is not known.他是否要来参加聚会还不知道。(引导词whether 在正常的陈述句语序的主语从句中不充当任何具体成分，只起引导作用) 考点名词性从句引导词的基本用法下表对高考中常见的名词性从句的引导词进行了总结：名词性从句的引导词引导词是否在名词性从句中充当成分的情况 连接代词： what, which, who, whom, whose 连接副词： when, where, why, how what, which在从句中作主语、 宾语、 表语或定语； who在从句中作主语、 表语； whom在从句中作宾语； whose在从句中作定语； whe
13、n, where, why, how在从句中分别作时间状语、 地点状语、原因状语/方式状语连词that否连词whether, if否名词性从句的引导词在高考中的基本用法详见下面的总结： 1. 引导特殊疑问句的疑问词在转为引导名词性从句时， 即成为连接代词(主要包括what, which, who, whom, whose)或者连接副词(主要包括when, where, why, how)。注意体会如下例句： Choose which you like best. 选你最喜欢的。/ Who has taken away my bag is unknown. 谁拿走了我的包还不知道。/ Havey
14、ou decided whom you are to nominate as your candidate? 你们是否已经决定提名谁做候选人了?/ He asked when Mr. Gilbert would be allowed to go home. 他问什么时候可以允许吉尔伯特先生回家。/ Where we can look up his address is still a problem. 我们在哪儿可以查到他的地址还是个难题。/ Why he did that wasnt quite clear. 他为什么做那件事还不十分清楚。/ How they will solve the
15、serious problem has not been decided. 他们将怎样解决这个严重问题还没有决定。以下两种特殊情况要给予特别关注： (1) what作连接代词引导的名词性从句既可以表示一个问“什么？”的问题，也可以表示相当于“名词/代词关系代词引导的定语从句”结构的意思， 这种特殊用法在语法上被称作“关系代词型的what”，注意体会如下例句：He is not what (=the person that) he was a few years ago. 他不是几年前的他了。/ This is what (=the place that) they call Salt Lake
16、 City. 这就是他们称作盐湖城的地方。/ What (=the place that) is now the North Sahara Desert was once a civilized world. 现在的北部撒哈拉沙漠曾是一个文明世界。/ Our income is now double what (=the income that) it was ten years ago. 我们现在的收入是十年前的两倍。/ The color of the flower is different from what (=the color that) it was in the morning. 花朵(现在的)颜色与它早上的颜色不同。 (2) 带ever后缀的疑问词除引导让步状语从句之外， 还可以引导名词性从句(“no matter疑问词”的结构只能引导让步状语从句， 不可以引导名词性从句)， 注意体会
