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关于it的用法： It可以作为代词，代替小孩、婴儿或不明身份的人，也可以是代替事物。例如：He made it absolutely clear. 他把此事讲得一清二楚。

It was one of the President's greatest accomplishments. 那是总统最伟大的成就之一。According to Mick, it's a great movie. 据米克说，这是一部了不起的电影。It was unfair to judge her on such a brief acquaintanceship. 你刚认识她就对她作出评价，这是不公平的。

高二英语下册第四单元Global warming语法知识点：it的用法如下：

⑴主语从句

① it is necessary ( important，natural，strange，)that

② it is a pity( a shame，no wonder)that

③ it is suggested(requested，proposed，desired)that

⑵宾语从句

suggest，propose，insist，demand，request，order，command，后

(4)it 可作形式主语或形式宾语。有以下几种不同的搭配关系：

①It + be +形容词+ that-从句 It is necessary that;It is important that;　It is obvious that…

② It + be + -ed 分词+ that-从句 It is believed that;　It is known to all that;It has been decided that;

③ It + be +名词+ that-从句It is common knowledge that…　……是常识

t is a surprise that…;It is a fact that…

④ It is + 名词/ 形容词 doing sth ( 用于 a waste， no good， no use，no point ，fun，

worthwhile，hard )

⑤ It is one’s turn to do sth.

⑥It takes sb. some time to do sth.

⑦It is not good to do sth.

⑧　It appears that;It happens that;It occurred to me that…

(5)It 也用于强调句结构：it is (was)+强调部分(主语、宾语或状语)+that(who)…的强调结构

(6)It is(high)time(that) 后用should ，但不可省should或者一般过去式。 例如：It's high time this leakage of information was put a stop to. 是结束这种泄密现象的时候了。It's high time you were able to get yourself up, my boy! 现在你应该可以不要人叫就自己起床了，我的孩子! It is high time for action. 该采取行动了。A quarrel was developing between husband and wife;it was high time I took myself off. 丈夫与妻子越吵越厉害，我该走开才是。

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