It用法及其句型和固定搭配讲解(1)
It 用法及其句型和固定搭配，是高中英语语法的重点、难点，又是近几年高考的热点，因此应给予充分的重视，现将it用法归纳如下：
一、It用作实词
表达以下概念：指代前文提到的事物，前文中的this，that；替代前文中的内容；指代一位性别不明的小孩或未知的人；指代未指明但谈话双方都知道的那件事；指代时间、天气、气候、距离等自然现象
二、It用作形式主语
替代作主语的从句、动词不定式、动名词，而把真正作主语的从句、动词不定式、动名词置于句尾。
It 作形式主语的常见句型：
1. 代作主语的动词不定式，其句型为
（1）It be adj.（for sb.）to do sth.
此处adj. 通常为描述事件的形容词：easy，difficult，hard，necessary，unnecessary，possible，impossible，likely，unlikely，right，wrong，important，unimportant，legal，illegal，well-mannered，ill-mannered，polite，impolite，clear，obvious，certain，suitable，proper，fit，useful，useless，dangerous
例 It is illegal（for a teenager）to drive a car without a license.
（2）It be adj. of sb. to do sth.
此处adj. 通常为描述人的形容词：kind，unkind，nice，rude，cruel，considerate，thoughtful，thoughtless，careful，careless，silly，foolish，stupid，clever，wise，crazy.
例 It's kind of you to help me with the problem.
（3）It替代作主语的动名词的常见句型
It's no good/use doing
It's（well）worth doing
It's（well）worth one's while doing/to do
It's（well）worth while doing/ to do
例 It's no use crying over spilt milk.
2. It替代作主语的从句常见句型
（1）It is + noun +从句
例 It is no secret that the president wants to have a second term at office.
（2）It is adj. +clause
It's surprising that（should） 竟然
It's a pity/shame that（should） 竟然
例 It's important that you should apologize to her for your rudeness.（=It's of much importance that you should apologize to her for your rudeness.）
（3）It verb sb. + clause= It is v-ing + clause
It+surprise/delight/interest/disappoint/worry/disturb/annoy/amaze
/bother/concern/frighten/please/anger sb. that
例 It worried me that she drove so fast.（= It was worrying that she drove so fast.）
（4）It verb（to sb.）that= sb/sth verb to do
（verb = appear，seem，come about，emerge，follow，chance，happen，occur，transpire，turn out ，work out）
例 It（so）happened/chanced that they were out.（= They happened/chanced to be out.）
（5）It is v-ed that=sb/sth is to do
（verb=say，report，think，believe，hope，expect，agree，accept，decide，determine，intend，plan，understand，know）
例 It is said that the couple have gotten divorced.（=The couple are said to have gotten divorced.）
（6）It is v-ed that （should）
（verb=demand，request，require，order，suggest，advise，recommend
例 It is suggested that they should begin with the third question.[1][2][3]