Section Ⅲ Grammar——名词性从句(Ⅱ)与it作形式主语
语 境 自 主 领 悟 先观察原句 ①That is why English has so many difficult rules that confuse people. ②It is interesting to learn how the words for animals and meat developed. ③It is certain that this process will continue... ④I always wondered when I would get the English novel my parents had promised to give me. ⑤What I always dreamt of has come true. ⑥It is fun wandering in the countryside. 后自主感悟 1.第①、④、⑤句中的黑体部分都是名词性从句，它们分别在各自的句子中作表语、宾语和主语。 2.第②、③、⑥句中的黑体部分都是it作形式主语的用法，it分别替代的是动词不定式、主语从句和动名词短语。
一、连接代词、连接副词引导的名词性从句
1．由what，which，who/whom，whose等连接代词和when，where，why，how等连接副词引导的名词性从句在句子中可以充当主语、宾语、表语或同位语。
(1)主语从句
What surprised us was her ignorance. 使我们吃惊的是她的无知。
Where we will go hasn't been decided. 我们要去哪儿还没有定下来。
When she will come is still unknown. 她何时来还不知道。 (2)宾语从句
The school was built on what used to be a wasteland. 这所学校是在以前的荒地上建造的。
Now we don't know how the pyramids were built. 现在我们不知道金字塔是如何建造的。 Please tell me whose book it is.
请告诉我这是谁的书。 (3)表语从句
The problem is how we could make him understand it. 问题是我们如何能使他明白这些。 The question is where we should go. 问题是我们应该去哪儿。
He was ill.That was why he didn't attend the meeting. 他病了。那就是他没出席会议的原因。
He didn't attend the meeting.That was because he was ill.他没出席会议。那是因为他生病了。
(4)同位语从句
I have no idea where he has gone. 我不知道他去哪里了。
We don't understand the problem why this is the best choice. 我们不明白这个问题——为什么这是最好的选择。 2．连接代词和连接副词的选择
连接代词和连接副词的选择要把握住两点：
(1)成分：连接代词在从句中作主语、宾语、表语或定语； 连接副词在从句中作状语。 (2)意义：无论是连接代词还是连接副词，通常都有各自的意义。 That's where the accident took place.
那就是事故发生的地方。(作状语，意为“……的地方”) She didn't know who/whom we were talking about. 她不知道我们在谈论谁。(作介词宾语，意为“谁”) [即时演练1]
选词填空：when，why，how，which，what，who，whom ①Do you know when the train arrives.
②Can you tell me why you chose the topic to write an article. ③How I can make greater progress later is a problem. ④Which team will win is not clear.
⑤What I want to know is who took away my book. ⑥The problem is whom we should have do it. 3．what与that的用法区别
(1)that只起连接作用，在从句中不充当任何成分，也无任何意义。
(2)what引导从句，除起连接作用外，还在从句中作主语、宾语、表语等成分，这时what
具有两个含义：
①保留疑问的意义，即“什么；什么样的”；
②相当于“the thing(s) that/which”，即“先行词＋定语从句”的含义。
另外，what的此种用法还可以表示时间(the time that)、地点(the place that)、人物(the person that)、数目(the amount/number that)等不同概念。
You can have what you like. 你喜欢什么就拿什么吧。
The trouble is that she has lost his address. 麻烦在于她弄丢了他的地址。
After what seemed a long wait，the results were announced. 经过了似乎漫长的等待之后，结果被宣布了。 [即时演练2] 单句改错
①That the professor said is of great importance. That→What
②The key is that we can get from it.that→what ③He saves that he earns.that→what
④I know the fact what he came here two years ago. what→that
4．“疑问词＋-ever”与“no matter＋疑问词”的用法区别
whoever，whatever，whichever等既可引导名词性从句又可引导让步状语从句，而“no matter＋疑问词”只能引导让步状语从句。
[即时演练3] 句型转换
①Anyone who comes here is welcome. →Whoever comes here is welcome. ②You can do anything you like. →You can do whatever you like. 二、it用作形式主语
当不定式、动名词、从句等用作主语时，为避免头重脚轻，通常在句首使用形式主语it，而把真正的主语放在句子末尾。
1．代替主语从句
it代替主语从句的常用句式如下：
(1)It be＋名词(a pity，a shame，an honour，a good idea，a miracle，a fact，common knowledge，a surprise ...)＋从句。
It is a pity that I can't go with you because I have to look after my little brother.
很遗憾我不能和你一起去，因为我必须照看我的弟弟。
It is common knowledge that the earth turns around the sun.地球围着太阳转是常识。
(2)It be＋形容词(clear，possible，likely，natural，certain，fortunate，necessary，strange，uncertain，obvious，important ...)＋从句。
It is obvious that they are for the plan. 很明显他们赞同此项计划。
(3)It＋不及物动词(happen，seem，appear，chance，occur，matter ...)＋从句。 It happened/chanced that I was in the countryside at the time.那时我恰巧在乡下。
It seems that it is going to rain soon. 看起来天马上要下雨了。
(4)It＋be＋过去分词 (found，believed，reported，thought，noted，proved，known，decided，suggested，required ...)＋从句。
It is reported that the fire caused a great loss and hundreds of people died. 据报道这一次火灾损失巨大并且数百人死亡。 [名师点津]
(1)“It＋be＋said/believed/reported/...that ...”句型一般可转换成“sb./sth.＋be said/believed/reported/...＋不定式”句型。
It is said that he has got a doctor's degree. ＝He is said to have got a doctor's degree. 据说他获得了博士学位。
(2)在句型“It＋is/was＋adj.＋主语从句”中，如果形容词是important，strange，natural，necessary等，从句谓语部分要用“should＋动词原形”形式，should可以省略。
It was necessary that we (should)make everything ready ahead of time. 我们有必要提前把一切都准备好。
(3)在“It is/was＋过去分词＋that...”结构中，如果动词是require，demand，request等，从句谓语部分要用“should＋动词原形”形式，should可以省略。
It is required that nobody (should) smoke here. 要求所有人都不能在这里吸烟。 2．代替不定式短语
It is hard to translate this sentence into English. 把这个句子译成英语很难。 3．代替v.-ing短语
It's no use arguing with him.同他争辩没用。 4．it作形式主语和it用于强调句型的比较
it作形式主语代替主语从句，主要是为了平衡句子结构，主语从句的连接词没有变化，可以是that，whether或连接代词、连接副词。而it强调句则是对句子某一部分进行强调，无论强调的是什么成分，都可用连词that，若被强调部分指人时也可用who。试比较：
It is a pity that you didn't go to see the film. 你没有去看电影真遗憾。(主语从句)
It doesn't interest me whether you succeed or not. 你成功与否我都不感兴趣。(主语从句)
It was in the morning that the murder took place. 正是上午的时候谋杀案发生了。(强调句型) It was John that/who broke the window. 是约翰把窗子打破的。(强调句型) [即时演练4] 用it作形式主语改写句子 ①To remember this rule is important. →It's important to remember this rule. ②Lying in the sun in winter is pleasant. →It is pleasant lying in the sun in winter. ③That her hair was turning grey worried her a bit. →It worried her a bit that her hair was turning grey.
Ⅰ.单句语法填空
1．What is important is how to persuade her to change her mind. 2．You may choose whatever topic you like to write your composition. 3．It is clear that the weather will soon turn out fine.
4．Occasions are quite rare when I have time to spend a day with my kids. 5．Whether ways will be found to stop pollution is just what worries the public. 6．－I prefer shutting myself in and listening to music all day on Sundays. －That's where I don't agree.You should have a more active life. 7．Whoever leaves the room ought to turn off the light.
8．He got killed in the accident.That's because he was careless.
9．It is very important that each of us pay attention to our English learning. 10．It remains to be seen that the newly formed committee's policy can be put
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