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

　　3．引导名词性从句的"疑问词­ever"与"no matter＋疑问词"的区别。

　　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。

　　Whoever telephones(＝No matter who telephones), tell them I'm out.

　　不管是谁打电话，就说我出去了。

　　No matter what you say, I believe you.

　　无论你说什么，我都相信你。

　　[即时演练4]　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.

　　我不能和你一起去真是太遗憾了，因为我必须照看我的弟弟。

　　It's a fact that most deaths from lung cancer are caused by smoking.

　　大部分肺癌导致的死亡是由吸烟引起的，这是个事实。

　　(2)It be＋形容词(clear, possible, likely, natural, certain, fortunate, necessary, strange, uncertain, obvious, important ...)＋从句。

　　It's clear (that) he has done his best.

　　很明显他已经尽力而为了。

　　(3)It＋be＋过去分词 (found, believed, reported, thought, noted, proved, known, decided, suggested, required ...)＋从句。

It is not yet decided who will do that job.