名词性从句主语从句、表语从句、宾语从句、同位语从句，在整个句子中所起的作用，相当于一个名词。因此，这四种从句通称为名词性从句。引导名词性从句的连接词可分为三类：连接词：that, whether, if （不充当从句的任何成分）连接代词：what, whatever, who, whoever, whom, whose, which.连接副词：when, where, how, why主语从句一、主语从句的概念与类型主语从句在复合句中作主句的主语,引导主语从句的词有从属连词that, whether以及连接代词who, what, which, whoever, whatever, whichever和连接副词when, where, why, how等.例如:That she was chosen made us very happy.她当选了使我们很高兴.What caused the accident is a complete mystery.是什么导致了这次事故还完全是一个谜.Whether she will come or not is still a question.她是否来还是一个问题.Which team will win the match is still unknown.哪个队会赢得这场比赛还不知道.Whoever comes to the party will receive a present.参加聚会的每一个人都将收到一份礼物.When they will start has not been decided yet.他们何时出发还没决定.注意:上述例句中的主语从句都是放在句首,但有时为了使句子结构平衡,避免头重脚轻,常用it作形式主语,而把从句放在后面.例如:It is a pity that she has made such a mistake.她犯了这样一个错误,真是遗憾.It depends on the climate whether they are going shopping today.他们是否今天去购物还得看天气情况.这样就构成了下面一些常用句型:1)It is + adj. / n. +从句It is a pity/shame that.遗憾的是It is possible that.很可能It is unlikely that.不可能2)It +不及物动词+从句It seems/appears that.似乎It happened that.碰巧3)It + be +过去分词+从句It is said that.据说It is known to all that.众所周知It is reported that.据报道It is believed that.据信;人们相信It is suggested that.有人建议It must be pointed out that.必须指出It has been proved that.已证明.例如:It is believed that at least a score of buildings were damaged or destroyed.据信,至少有二十座楼房遭到破坏或彻底毁掉.It is suggested that the meeting should be put off.有人建议会议延期召开.Its reported that three people were killed in the accident and five were hurt badly.据报道,事故中三人丧生,五人重伤.It is known to all that Taiwan is an inseparable part of China.众所周知,台湾是中国不可分割的一部分.巩固练习1. Does _ matter if he cant finish the job on time? A. this B. that C. he D. it2. It worried her a bit _ her hair was turning grey. A. which B. that C. if D. for3. _ is a fact that English is being accepted as an international language.A. There B. This C. That D. It二、学习主语从句应该注意的几个问题1)引导词that与whatwhat既有引导主语从句的作用,同时又在从句中作句子成分(主语、宾语、表语等).这时what相当于all that/everything that.,常译成所的(东西、事情、话等.);而that只起连接作用,本身无实际意义,在从句中也不担当任何句子成分.但that引导的主语从句放在句首时,不能省略that.例如:What is done cant be undone. (谚语)已成定局,无可挽回.What we cant get seems better than what we have.我们得不到的东西似乎比已得到的要好.That we should work out a plan to deal with the present serious situation is important.我们应该制定一项计划来应付目前严峻的形势,这一点非常重要.That a new teacher will come to teach us geography is true.一位新老师将来教我们地理,这是真的.巩固练习4. _ what they told me really true?A. Has B. Is C. Does D. Have5. It matters little _ a man dies, but _ matters much is _ he lives.A. how; what; how B. how; it; how C. why; it; why D. that; what; that6. _ she couldnt understand was _ fewer and fewer students showed interest in her lessons. A. What; why B. That; what C. What; because D. Why; that7. It is pretty well understood _ controls the flow of carbon dioxide in and out the atmosphere today. A. that B. when C. what D. how8. _ fashion differs from country to country may reflect the cultural differences from one aspect. A. What B. That C. This D. Which9. -What made her parents so angry?- _ she had failed in the examination.A. As B. Because C. Since D. That2)引导词if和whetherif和whether引导动词后的宾语从句时一般可通用,但介词后的宾语从句、主语从句(放在句首时)、表语从句常由whether引导.例如:Whether she will go home or not is unknown.她是否回家还不得而知. Whether we shall raise ducks or geese remains to be decided.我们是养鸭还是养鹅仍没决定.=It remains to be decided whether/if we shall raise ducks or geese.但我们不能说If we shall raise ducks or geese remains to be decided.巩固练习10. _ well go camping tomorrow depends on the weather. A. If B. Whether C. That D. Where 3)其它引导词连接代词who, which, whom, whose有各自的意义,起连接作用,并在从句中充当语、宾语、表语、定语等;连接副词when,where, why, how等有各自的意义,起连接作用,并在从句中充当状语.巩固练习11. -Do you remember _ he came? -Yes, I do. He came by car.A. how B. when C. that D. if12. It was a matter of _ would take the position. A. who B. whose C. whom D. whomever13. -I drove to Zhuhai for the air show last week.-Is that _ you had a few days off?A. why B. when C. what D. where14. I read about it in some book or other, does it matter _ it was? A. where B. what C. how D. which三、语气在It is necessary / natural / important / strange.+ that-clause这类句型里,that所引导的主语从句中谓语动词用should +原形,表虚似语气.例如:It is necessary that the problem should be settled at once.这个问题必须马上解决.Its strange that he should have gone away without telling us.他竟然没向我们说一声就走了,真是奇怪.巩固练习15. It is necessary that a college student _ at least a foreign language. A. masters B. should master C. mastered D. will master四、以it作形式主语的主