一、概述：在句子中起名詞作用的各種從句統(tǒng)稱為名詞性從句。根據(jù)它們在句中的語法作用，這類從句又可分為主語從句、同位語從句、表語從句和賓語從句。? 二.主語從句主要有四類：

　　（1） 由連詞that引導(dǎo)的主語從句:引導(dǎo)詞that無含義/在句中不做成分/不可以省。 例如：That you will win the medal seems unlikely.

　　That you are so indifferent bothers me.

　　That she survived the accident is a miracle. （2） 用連詞 whether 引導(dǎo)的主語從句:

　　whether有含義(是否)/在句中不做成分/不可以省。

　　注意：引導(dǎo)主語從句，不能用if，只能用whether。

　　例如：Whether we will hold a party in the open air tomorrow depends on the weather.

　　Whether she is coming or not doesn’t matter too much. （3） 用連接代詞引導(dǎo)的主語從句

　　在由連接代詞who, whose, whom, which, what, whoever, whomever, whichever, whatever引導(dǎo)的名詞性從句中，其連接代詞在句中起名詞性作用，擔(dān)當(dāng)一定成分. 例如：What you need is more practice.

　　What I want to know is this.

　　Whatever we do is to serve the people. 注：whatever / whoever的功用

　　whatever, whoever在主語從句中不含疑問意義。它引導(dǎo)主語從句，并在從句中作主語、賓語、表語等。whatever = anything that; whoever = anyone who。要注意和whatever, whoever引導(dǎo)的讓步狀語從句的區(qū)別。

　　如： Whoever breaks the law should be punished. （主語從句）

　　（ ＝Anyone who breaks the law should be punished. ）

　　Whoever breaks the law, he should be punished. （讓步狀語從句）

　　（ ＝No matter who breaks the law, he should be punished. ）

　　（4）用連接副詞when, where, why, how引導(dǎo)的名詞性從句(其連接副詞有含義,在句中作狀語。)

　　例如:Where we should leave it is a problem.

　　When they will come hasn’t been made pubic. 三.由 it構(gòu)成的主語從句

　　（1）由連詞that引導(dǎo)的主語從句，在大多數(shù)情況下會放到句子的后面，而用代詞it作形式主語。

　　例如：That light travels in straight lines is known to all.

　　=It is known to all that light travels in straight lines.

　　When the plane is to take off has not been announced .

　　= It has not been announced when the plane is to take off. (但當(dāng)what引導(dǎo)的主語從句表示“…的東西”時，一般不用it作形式主語。) 錯:It is a book what he wants. 對:What he wants is a book. 另外，需要注意的是，it作形式主語代替主語從句時，要注意和as引導(dǎo)的定語從句的區(qū)別。試比較：

　　It was reported that the US was under the terrorist attack.

　　As was reported, the US was under the terrorist attack.

　　（2）常見用it作形式主語的復(fù)合句結(jié)構(gòu)

　　It is +名詞+從句

　　It is a fact that… 事實(shí)是……

　　It is good news that … ……是好消息

　　It is a question that … ……是個問題

　　It is common knowledge that … ……是常識

　　類似的名詞還有：a pity；a wonder；a good thing； no wonder； surprise等。

　　例如：It is a mystery to me how it all happened.

　　It is common knowledge that the whale is not a fish.

　　It is no surprise that Bob should have won the game.

　　It’s a pity that you missed the film.

　　 It is +形容詞+從句 It is necessary that … 有必要…… It is clear that … 很清楚…… It is likely that … 很可能…… It is important that … 重要的是…… 類似的形容詞還有：strange; natural; obvious; true; good; wonderful; possible; unlikely; quite;

　　unusual; certain; evident; worth-while; surprising; interesting; astonishing, etc. 例如：It is doubtful whether she will be able to come.

　　It was really astonishing that he refused to talk to you.

　　It is essential that he should be here by the weekend.

　　It seems obvious that we can not go on like this.

　　It is necessary that you （should）master the computer.

　　It is important that a student learn English well.

　　It’s clear that they badly need help.

　　It is likely that a hurricane will arrive soon.

　　需要注意的是，這類主語從句中，謂語動詞很多為“（should）＋動詞原形”，即要用虛擬語氣。

　　It is +過去分詞+從句 It is said that … 據(jù)說…… It is reported that … 據(jù)報道…… It has been proved that … 已證明…… It must be proved that… 必須指出…… 類似的過去分詞還有：known; estimated; expected; believed; thought; hoped; noted; discussed; required; decided; suggested; demanded; made clear; found out,etc. 例如：It is thought that he is the best player.

　　It is estimated that the vase is 2000 years old.

　　It is used to be thought that a new star must be due to a collision between two stars.

　　It has not been made clear when the new road is to be opened to traffic.

　　It is said that he was killed in the earthquake.

　　It seems （happened / appears / doesn’t matter / makes no difference / occurred …）that …如：

　　It seems that they will win the game.

　　It makes no difference whether he will attend the meeting or not.

　　It does not matter if I missed my train. It happened that I saw him yesterday.

　　一、概述：在句子中起名詞作用的各種從句統(tǒng)稱為名詞性從句。根據(jù)它們在句中的語法作用，這類從句又可分為主語從句、同位語從句、表語從句和賓語從句。? 二.主語從句主要有四類：

　　（1） 由連詞that引導(dǎo)的主語從句:引導(dǎo)詞that無含義/在句中不做成分/不可以省。 例如：That you will win the medal seems unlikely.

　　That you are so indifferent bothers me.

　　That she survived the accident is a miracle. （2） 用連詞 whether 引導(dǎo)的主語從句:

　　whether有含義(是否)/在句中不做成分/不可以省。

　　注意：引導(dǎo)主語從句，不能用if，只能用whether。

　　例如：Whether we will hold a party in the open air tomorrow depends on the weather.

　　Whether she is coming or not doesn’t matter too much. （3） 用連接代詞引導(dǎo)的主語從句

　　在由連接代詞who, whose, whom, which, what, whoever, whomever, whichever, whatever引導(dǎo)的名詞性從句中，其連接代詞在句中起名詞性作用，擔(dān)當(dāng)一定成分. 例如：What you need is more practice.

　　What I want to know is this.

　　Whatever we do is to serve the people. 注：whatever / whoever的功用

　　whatever, whoever在主語從句中不含疑問意義。它引導(dǎo)主語從句，并在從句中作主語、賓語、表語等。whatever = anything that; whoever = anyone who。要注意和whatever, whoever引導(dǎo)的讓步狀語從句的區(qū)別。

　　如： Whoever breaks the law should be punished. （主語從句）

　　（ ＝Anyone who breaks the law should be punished. ）

　　Whoever breaks the law, he should be punished. （讓步狀語從句）

　　（ ＝No matter who breaks the law, he should be punished. ）

　　（4）用連接副詞when, where, why, how引導(dǎo)的名詞性從句(其連接副詞有含義,在句中作狀語。)

　　例如:Where we should leave it is a problem.

　　When they will come hasn’t been made pubic. 三.由 it構(gòu)成的主語從句

　　（1）由連詞that引導(dǎo)的主語從句，在大多數(shù)情況下會放到句子的后面，而用代詞it作形式主語。

　　例如：That light travels in straight lines is known to all.

　　=It is known to all that light travels in straight lines.

　　When the plane is to take off has not been announced .

　　= It has not been announced when the plane is to take off. (但當(dāng)what引導(dǎo)的主語從句表示“…的東西”時，一般不用it作形式主語。) 錯:It is a book what he wants. 對:What he wants is a book. 另外，需要注意的是，it作形式主語代替主語從句時，要注意和as引導(dǎo)的定語從句的區(qū)別。試比較：

　　It was reported that the US was under the terrorist attack.

　　As was reported, the US was under the terrorist attack.

　　（2）常見用it作形式主語的復(fù)合句結(jié)構(gòu)

　　It is +名詞+從句

　　It is a fact that… 事實(shí)是……

　　It is good news that … ……是好消息

　　It is a question that … ……是個問題

　　It is common knowledge that … ……是常識

　　類似的名詞還有：a pity；a wonder；a good thing； no wonder； surprise等。

　　例如：It is a mystery to me how it all happened.

　　It is common knowledge that the whale is not a fish.

　　It is no surprise that Bob should have won the game.

　　It’s a pity that you missed the film.

　　 It is +形容詞+從句 It is necessary that … 有必要…… It is clear that … 很清楚…… It is likely that … 很可能…… It is important that … 重要的是…… 類似的形容詞還有：strange; natural; obvious; true; good; wonderful; possible; unlikely; quite;

　　unusual; certain; evident; worth-while; surprising; interesting; astonishing, etc. 例如：It is doubtful whether she will be able to come.

　　It was really astonishing that he refused to talk to you.

　　It is essential that he should be here by the weekend.

　　It seems obvious that we can not go on like this.

　　It is necessary that you （should）master the computer.

　　It is important that a student learn English well.

　　It’s clear that they badly need help.

　　It is likely that a hurricane will arrive soon.

　　需要注意的是，這類主語從句中，謂語動詞很多為“（should）＋動詞原形”，即要用虛擬語氣。

　　It is +過去分詞+從句 It is said that … 據(jù)說…… It is reported that … 據(jù)報道…… It has been proved that … 已證明…… It must be proved that… 必須指出…… 類似的過去分詞還有：known; estimated; expected; believed; thought; hoped; noted; discussed; required; decided; suggested; demanded; made clear; found out,etc. 例如：It is thought that he is the best player.

　　It is estimated that the vase is 2000 years old.

　　It is used to be thought that a new star must be due to a collision between two stars.

　　It has not been made clear when the new road is to be opened to traffic.

　　It is said that he was killed in the earthquake.

　　It seems （happened / appears / doesn’t matter / makes no difference / occurred …）that …如：

　　It seems that they will win the game.

　　It makes no difference whether he will attend the meeting or not.

　　It does not matter if I missed my train. It happened that I saw him yesterday.