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1、,It做形式主语, Its necessary for the young to master two foreign language., Its a waste of time talking to her any more., Its a pity that you missed the exciting football match.,动词不定式,动名词,从 句,形式主语,It 作为形式主语的用法,当 不定式、动名词、从句 等用作句子主语时，为保持句子平衡，通常把真正的主语放在句末，而在句首使用形式主语it.,拒绝是令人遗憾的.,记住这一点是很重要的.,Its a pity to re
2、fuse.,Its very improtant to remember this,一、代替动词不定式做形式主语,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，impossible， important，natural, likely，obvious，useful，useless，dangerous做某事是 Its necessary for us to master a foreign language.,It +be+ adj.+ of sb. to do sth 此处ad
3、j. 通常为描述人的形容词：kind，nice，rude，cruel，careless，foolish，stupid，wise，crazy某人做某事，某人是 eg. Its foolish of you to drive a car after drinking. Its very kind of you to help me with my English.,It + be +名词词组+动词不定式 eg. It is not a good habit to stay up too late. 常见句型： It takes/took sb. some time/money to do sth.
4、,It is no good crying over spilt milk.,It is no use casting pearls before swine .,覆水难收,不要明珠暗投，对牛弹琴,构成如下结构： It is +no use/no good/not any good/not any use+ doing sth.,二、代替动名词作形式主语,It + be + 名词词组 + 主语从句 这类名词有：a fact, a pity, a shame, an honour，a question，a surprise，common knowledge eg.Its common knowl
5、edge that people cannt live without water .,三、代替从句做形式主语,It + 不及物动词 + that（as if）-从句 这类不及物动词有：look，seem，appear，happen，occur eg.It seems that he does not tell the truth.,It is time +that sb. +v-ed/ should do Eg. Its time that you went to bed Its time that you should go to bed. Its necessary/ impossibl
6、e/ important/ natural that sb. (should) do Eg. Its important that we (should) keep the balance of nature.,It + be +adj.+that-从句,It + be +-ed（过去分词）+ that-从句,It is said that 据说 It is reported that 据报道 It is supposed that 据推测 It is hoped that 希望 It is well known that 众所周知 It is generally considered that普遍认为 It is suggested that 有人建议,练习：把下列格局转换为it做形式主语的句子,1.He was rude to say so. 2.Trying again is of use. 3.When and where to hold the party hasnt been decided.,It was rude of him to say so.,It is of use trying again.,It hasnt been decided when and where to hold the party.,Thank you .,