英语中It引导的结构用法小结

It 既是 代词又是引词。作代词时，它可做人称代词、指示代词、非人称代词，用于前指、非确指或习语中。

it作引词时，它本身无实义，只起先行引导的作用。可作 形式主语（it is + adj. + for/of sb. to do sth.）或 形式宾语（it + adj. + to do sth.），真实的主语或宾语是 不定式、 动名词或名词 从句，它们则放在后面。It 也用于 强调句结构。

如想强调某个词或部分，可用it is (was) + 强调部分（主语、宾语或状语） + that(who）…的强调结构。本章要求了解代词it 和引词it 的各种用法，重点掌握it 用于前指或后指；引导词it 用于强调结构。

例：It is Tom’s sister who have had won the first place in the 100 meter race.

注意：

有时为避免句子头重脚轻，常用形式主语it代替 主语从句作形式主语放于句首，而把主语从句置于句末。主语从句后的 谓语动词一般用单数形式。常用句型如下：

It is necessary (important, natural, strange, etc.) that …

It is suggested (requested, proposed, desired, etc.) that…

That- 从句做主语通常用it作先行词，而将that-从句置于句末，例如：

It is quite clear that the whole project is doomed to failure. 很清楚，整个计划注定要失败。

It's a pity that you should have to leave. 你非走不可真是件憾事。

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用it作 形式主语的that-从句有以下四种不同的搭配关系：

a. It + be +形容词+ that-从句

It is necessary that…　有必要……   /   It is important that…　重要的是……

It is obvious that…　很明显……

例：It is significant for persons to learn English well !

b. It + be + -ed 分词+ that-从句

It is believed that…　人们相信……

It is believed that to get a high education degree that can lead to a better salary . 人们相信获得更高的学历水平可以得到跟更高的薪水。

It is known to all that…　众所周知……

It is known to all that the Beijing is the Chinese capital .   众所周知北京是中国的首都

It has been decided that…　已决定……

It has been decided that Sunny will hold the meeting and give a speech .已经决定让Sunny主持会议并发表演讲。

c. It + be +名词+ that-从句

It is common knowledge that…　……是常识 /  It is a surprise that…　令人惊奇的是……

It is a fact that…　事实是……

It is a fact that the Taiwan Island belongs to China form thousands years ago.

d. It +不及物动词+ that-从句

It appears that…　似乎……   /    It happens that…　碰巧……

It occurred to me that…　我突然想起……

It occurred to me that I have left my purse behind at home .

It's for sb.和 It's of sb.

1）  for sb. 常用于表示事物的特征特点，表示客观形式的形容词，如easy, hard, difficult, interesting, impossible等：

It's very hard for him to study two languages. 对他来说学两门外语是很难的。

2）of sb的句型一般用表示人物的性格，品德，表示主观感情或态度的形容词，如good, kind, nice, clever, foolish, right。

It's very nice of you to help me. 你来帮助我，你真是太好了。

It作为引导词，引导长句时候非常普遍，并且对于不会运用其他几个复杂的从句的英语学员来说，是展示语法功底的优势手段。基本句型按照套路即可全部掌握。