It做形式主语讲解

二、代替动名词作形式主语
It is no good crying over spilt milk. 覆水难收
It is no use casting pearls before swine . 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.
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.
一、代替动词不定式做形式主语
拒绝是令人遗憾的. It’s a pity to refuse.
记住这一点是很重要的. It’s very improtant to remember this
natural that sb. (should) do • Eg. It’s important that we (should) keep
the balance of nature.
④It + 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
①It +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…
1.He was rude to say so. It was rude of him to say so.
2.Trying again is of use. It is of use trying again.
3.When and where to hold the party hasn’t been decided.
It hasn’t been decided when and where to hold the party.
Thank you .
三、代替从句做形式主语
①It + 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.It’s common knowledge that people cann’t live without water .
• It’s very kind of you to help me with my English.
③It + 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.
It’s necessary for us to master a foreign language.
• ②It +be+ adj.+ of sb. to do sth
• 此处adj. 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. It’s foolish of you to drive a car after drinking.
来自百度文库It做形式主语
❤ It’s necessary for the young to master two foreign language.
动词不定式
形式主语 ❤ It’s a waste of time talking to her any
more. 动名词
❤ It’s a pity that you missed the exciting football match. 从 句
②It + 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.
③It + be +adj.+that-从句
• It is time +that sb. +v-ed/ should do • Eg. It’s time that you went to bed • It’s time that you should go to bed. • It’s necessary/ impossible/ important/