语法讲义——名词性从句
一、复合句的定义：复合句又称主从复合句，由一个主句和一个或一个以上的从句构成，主句为句子的主体，从句不能独立，只用作句子的一个成分。从句担任哪个句子成分，这个从句就叫做该成分的从句。
二、名词性从句：主语从句、表语从句、宾语从句、同位语从句。
引导词

功 能
例 词
从属连词
只起连接作用，不充当从句的任何成分
that whether if
连接代词
既起连接作用，本身又作从句的主、宾、
表、定
who whom what which whose whateverwhichever whoever
连接副词
既起连接作用，本身又作从句的状语
when where how why whenever wherever
㈠主语从句
1、that 引导的主从（that 在主从中无任何意义，也不充当任何成分，通常不能省略）
●在正式文中，为了强调that 引导的主从，that 可以置于句首，在这种情况下，that 不可省
e.g: 很明显，司机不能控制他的车。That the driver could not control his car was obvious.
她被选中使我们非常高兴。 That she was chosen made us very happy.
●在通常情况下，用it 作形式主语，而将that 从句置于句尾。此时that 有时可省
（改写上文两个例句） It was obvious that the driver could not control his car.
It made us very happy that she was chosen.
●如果that 从句是疑问句，只能用it 作形式主语结构
e.g Is it certain that he will come?
It it true that he would take the risk?
●it 作形式主语置于句首时，常用结构：
☆It + be + adj. + that 从句
很可能他会来。 It is likely that he will come.
真奇怪她曾经信任他. It is strange that she has ever trusted him.
☆It + be + n. 词组 + that 从句
鲸鱼不是鱼，这是常识。 It is common knowledge that the whale is not a fish.
他竟然错过了火车，真是遗憾。 It is a pity that he should have missed the train.
难怪他看起来如此迷惑。 It’s no wonder that he looks so puzzled.
（在表示惊讶、喜悦、遗憾等感情色彩时，that 分句中的谓语动词常用should）
☆It + be + p.p.（said, reported, hoped, known, believed etc.）+ that 从句
据说他是一个著名的作家。 It is said that he is a famous writer.
据报道今天下午有一场暴风雨。 It is reported that there will be a storm this afternoon.
☆It +seem/ happen/ appear 等不及物动词 + that 从句
似乎他错了。 It seems that he is wrong.
好象他们现在急需帮助。 It now appears that they are in urgent need of help.
2、whether 引导的主从，意为“是否”（if 不能引导主语从句）
他是否会赢得这场比赛，还不清楚。Whether he will win the game is not clear.
她来不来与我无关。 Whether she comes or not doesn’t concern me.
从句在句首时，必用whether， 在句尾时，有时可用if .
e.g: It is not clear whether/ if he will come.
3、wh-疑问词引导主语从句
他为什么做这件事还不知道。Why he did this is not known.
它是谁的书并不重要。 Whose book it is not important.
他什么时候会回来还不知道。When he will return is still unknown.
谁为这次事故负责还不清楚。Who was responsible for the accident is not yet clear.
（wh-引导的主语从句也常用it 作形式主语的句式中）
e.g: It is not known why he did this.
4、也可以用whatever, whoever, whomever, whenever, wherever等词引导主语从句
无论谁告诉你那件事都是在撒谎。 Whoever told you that was lying.

※看2001年的一道高考题：
_____ is known to everybody, the moon travels round the earth once every month.
A. It B. As C. That D. What
分析：此题很多考生误选了A 或C，其原因是没有注意到逗号的作用。句中逗号已表明该句不是主语从句，而是as引导的非限制性定语从句。故答案为B.
※上海’99年的一道高考题：
_____ has helped to save the drowning girl is worth praising.
A. Who B. The one C. Anyone D. Whoever
分析：此题答案为D。“疑问词+ever”构成的复合连接词（however除外）既可以引导名词性从句（主从、表从、宾从、同位语从句），也可以引导让步状语从句。而“no matter + 疑问词”只能引导让步状语从句。二者引导让步状语从句时可以互换，引导名词性从句时只能用“疑问词+ever”形式。
㈡表语从句
1、that 引导的表语从句无任何意义，不充当任何句子成分，通常不省略
● 表示事实、真理等的实际内容
事实是他在撒谎。 The fact is that he is lying.
●表示某人的意见、信念等的实际内容
我们的信念是一切都会好转的。 Our belief is that things will improve.
麻烦是我们缺少资金。 The trouble is that we are short of money.
2、whether引导（此时通常不可用if 代替whether.）
问题是人们是否会买它。 The question is whether people will buy it.
3、wh-引导
那只铅笔在它原先放的地方。 The pencil is where it was.
问题是我们应该去哪。 The question is where we should go.
4、as if, as though 引导，可用真实语气也可用虚拟语气
他看起来好象生气了。 He looks as if he were angry.
他看起来好象要哭了。 He looks as if he were going to cry.
㈢宾语从句
1、that 引导从句无意义，不充当任何成分，常省略。
（动词后有两个宾语从句第二个that不可省）
e.g: I know (that) you have met him and that you have become good friends.
●经常在动词和宾语从句之间插一个间接宾语（人）。
他告诉我他错了。 He told me that he was wrong.
●在动词think , believe, suppose, expect, guess等后面的宾语从句中的否定前移
e.g: I don’t think you are right.
I
生词表: