'tI形式主语
Examples:
1. It' necessary for the young to master two foreign language
2. It is no use arguing about the matter with him
3. It'a pity that you fail the exam.
It用作形式主语
当不定式（短语）、动名词（短语）或从句在某个句子中作主语时，为保持句子结构前后平衡，避免头重脚轻，因此常用it作形式主语置于句首，而将真正的主语放在句尾。
此时it只起先行引导作用，本身无词义。
一、代替动词不定式做主语
拒绝是令人遗憾的。
It 'a pity to refuse.
记住这点是很重要的。
It 'very importa nt to remember this point.
1. It + be + 形容词+ for sb + to do sth
这类句型常用形容词（通常为描述事件的形容词）easy, difficult, hard,
important, possiblewise, necessary, impossible, likel y, obvious, use 等作表语，有时候为了强调不定式动作的执行者，常在不定式前加for sb,译为“对某人来说做某事怎么样”
It ' s necessary for the young to master two foreign Ianguages.
It is unwise to give the children whatever they want.
2. It + be + 形容词+ of sb. + to do s_jh
这类形容词常是表示心理品质，性格特征的形容词，如：kind, nice stupid,
clever, foolish, polite, impolite, silly, selfish, con siderate等。
某人和这些形容词可以构成主系表结构。
It ' s very kind of you to help me with the work.
=You are kind to help mewith the work.
It s foolish of you to drive a car after drinking.
=You are foolish to drive a car after drinking.
3. It + be +名词词纟组+ to do sth
It is not a good habit to stay up too late.
4. It takes/took sb +some time/ money to do st做某事花了某人多长时间或多少钱
It took the workers almost three years to finish building the dam.
It will take a whole day to get to the top of the mountain on foot.
二、it代替动名词做形式主语
It is no good use 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）
It + be +名词或形容词+ 动名词
这类名词和形容词常常是：good, no good, no use, a waste of…,useless,
sen seless等
It s' a waste of time talking to her any mora
It is no use arguing about the matter with him.
三、it代替从句做主语
1. it + be + 名词词组+ 主语从句
这类名词有： a fact, a pity, a shame, an honor, a question, aurprise ……
It s a pity that you lose your money
2. it + 不及物动词+ that(as if )+ 从句
这类不及物动词有：look, seem, appear, happe n, occur,
It seems that he does not tell the truth.
It occurs to me that I forgot to lock the door!我突然想起我忘记锁门了
3. it + be + adj + tha从句
It is necessary/impossible/important/natural that sb. (should) do sth.
It 'important that we (should) keep the balanee of nature
4. 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 well known that ...... 众所周知
it is gen erally con sidered that … 普遍认为it is suggested that 有人建议实战演练：
1. It is gen erally con sidered un wise to give ____ a child he or she wan ts.
A. however
B. whatever
C. whichever
D. whe never
2. I n fact __ is a hard job for the police to keep order in an importa nt football
match.
A. this
B. that
C. there
D. it
3. ___ i s a fact that En glish is being accepted as an intern ati on al la nguage.
A. There
B. This
C. That
D. It
4. Is ______ n ecessary to take off our shoes whe n we en ter the lab?
A. every one
B. this
C. her
D. it
5. _______ will take you a lot of time to find him in the crowd.
A. It
B. I
C. We
D. They
6. It is no use his ________ there, the situati on is hopeless now.
A. to go
B. to be going
C. going
D. hav ing gone
7. It is never too late to learn, _______ ?
A. is it
B. isn ' t it
C. does it
D. doesn ' t it
8. _________ is known to all that Shenzhou VI Launched Successfully.
A. As
B. What
C. It
D. That
9. _____ is reported in the newspaper, the Earthquake in east China's Jiangxi Province killed 13 people
A. It
B. As
C. That
D. What
10. _________ certain that his invention will make people 'lifse convenient.
A. That ' s
B. This is
C. It ' s
D. What ' s
11. _______ that there is another football match on the air this evening.
A. It says
B. It was said
C. It is said
D. What was said
12. ________ that their daughter got an opportunity to study abroad.
A. It ' s a exciting news
B. This is an exciting news
C.This is exiting news
D. It ' s exciting news。