常用it作形式主语地句型结构

常用it作形式主语的句型结构◇It + be +形容词+ that-从句可用于此句型的形容词有: wonderful, true，good，right，wrong，（un）important，useless，surprising，clear，unusual，lucky，certain, necessary等。

如：①It is quite certain that he will be at the meeting.②It is surprising that he came late to school this morning.③It is important that we (should) study hard注意: 该句型中的形容词是（un）important, necessary等时，从句应为(should )+动词原形。

◇It + be + -ed 分词+ that-从句适用该句型的过去分词主要有: said, reported, announced, hoped, thought，told，believed，expected，decided，suggested, known等。

如：①It is hoped that one day they will have enough animals to set them free②It is well known that the earth goes around the sun.③It is suggested that the sports meeting (should ) be put off until next week.注意: 该句型的过去分词是suggested时，从句应为(should )+动词原形。

◇It + be +名词+ that-从句适用该句型的名词（词组）有: a pity，an honor，a good thing，a fact，a surprise，good news, one’s duty等。

如：①It is a pity (that) you missed the sports meeting last week.②It is a fact that English is being accepted as an international language.◇It ＋seem／ appear／ happen的适当形式＋that从句。

该句型常可以转换成含不定式的简单句。

如：①It seems that there is a big waste pipe coming down from the town.→There seems to be a big waste pipe coming down from the town.②He appeared to becalm, but inside his heart was beating wildly with fear.→It appeared that he was calm, but inside his heart was beating wildly with fear.◇It doesn't matter ( It’s no wonder; It doesn’t make much difference等)＋ when/ where/ which/ whether 等从句。

如：①Does it matter if he can't finish the job on time②They are all classmates. It is no wonderthey should help each other with their studies.◇It + be + adj./ n. (for sb. / of sb.) + to do sth. 该句型中的形容词通常是表示事物的特点或特征的如difficult，hard，easy，impossible，necessary，important等，此时用for；或表示人的性格特征或特点的如nice，good，bad，kind，silly，foolish，wise，clever， careless，rude，brave，cruel，careful， grateful等，这时要用 of。

如：①It is foolish of you to give up such a good chance.②It is necessary for college students to master at least a foreign languageIt作形式主语常见句型动词不定式，动名词或主语从句作主语时，通常把它们放在谓语动词前，而用it 作形式主语，放到句首，常见句型有：1. It + be +形容词+主语从句，如：It is uncertain whether he can come to Jenny’s birthday party or not.2. 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等，如：It’s a pity that you missed the exciting football match.It remains a question whether he will come or not.3. It + be +过去分词+主语从句，这类过去分词有：announced, believed, expected, hoped, decided, reported, said, shown等，如：It is reported that 16 people were killed in the earthquake.It is not decided who will give the operation to the patient.4. It +不及物动词(seem, appear, happen等) +主语从句,这类不及物动词有：appear, happen, seem等，如：It seemed that he didn’t tell the truth.It happened that I was out when he called.5. It + be +形容词+ for sb.）+动词不定式这类句型常用形容词easy, difficult, hard, important, possible，wise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，如：It’s necessary for the young to master two foreign language.It is unwise to give the children whatever they want.这类形容词有：easy, difficult, hard, important, possible，wise6. It + be +形容词+ of sb. +动词不定式，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, considerate等。

某人和这些形容词可以构成主系表结构。

如：It’s very kind of you to help me with the work.=You are kind to help me.It seemed selfish of him not to share his dictionary with others.=He seemed selfish not to share his dictionary with others.7. It + be +名词词组+动词不定式，如：It is not a good habit to stay up too late.8. 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, senseless等，如：It’s a waste of time talking to her any more.It is no use arguing about the matter with him.9. It + take ( sb. )+时间（金钱）+动词不定式，如：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.实战演练：1. It is generally considered unwise to give a child he or she wants. (NMET 1997)A. howeverB. whateverC. whicheverD. whenever2. In fact is a hard job for the police to keep order in an important football match. (2001上海)A. thisB. thatC. thereD. it3. is a fact that English is being accepted as an international language. (NMET1995)A. ThereB. ThisC. ThatD. It4. Is necessary to take off our shoes when we enter the lab (MET88)A. everyoneB. thisC. herD. it5. ________ will take you a lot of time to find him in the crowd.A. ItB. IC. WeD. They6. It is no use his _________ there, the situation is hopeless now.A. to goB. to be goingC. goingD. having gone7. It is never too late to learn, ________A. is itB. isn’t itC. does itD. doesn’t it8. ___________ is known to all that Shenzhou VI Launched Successfully.A. AsB. WhatC.ItD. That9. _______ is reported in the newspaper,the Earthquake in east China's Jiangxi Province killed 13 peopleA. ItB. AsC. ThatD. What10. ___________ certain that his invention will make people’s life convenient.A. That’sB. This isC. It’sD. What’s11. _________ that there is another football match on the air this evening.A. It saysB. It was saidC. It is saidD. What was said12. __________ that their daughter got an opportunity to study abroad.A. It’s a exciting newsB. This is an exciting newsC. This is exiting newsD. It’s exciting news参考答案：1——5 BDDDA 6——10CACAC 11——12CD一、主语从句的概念与类型主语从句在复合句中作主句的主语,引导主语从句的词有从属连词that, whether以及连接代词who, what, which, whoever, whatever, whichever和连接副词when, where, why, how等.例如:That she was chosen made us very happy.她当选了使我们很高兴.What caused the accident is a complete mystery.是什么导致了这次事故还完全是一个谜.Whether she will come or not is still a question.她是否来还是一个问题.Which team will win the match is still unknown.哪个队会赢得这场比赛还不知道.Whoever comes to the party will receive a present.参加聚会的每一个人都将收到一份礼物.When they will start has not been decided yet.他们何时出发还没决定.注意:上述例句中的主语从句都是放在句首,但有时为了使句子结构平衡,避免"头重脚轻",常用it作形式主语,而把从句放在后面.例如:It is a pity that she has made such a mistake.她犯了这样一个错误,真是遗憾.It depends on the climate whether they are going shopping today.他们是否今天去购物还得看天气情况.这样就构成了下面一些常用句型:1)It is + adj. / n. +从句It is a pity/shame that...遗憾的是……It is possible that...很可能……It is unlikely that...不可能……2)It +不及物动词+从句It seems/appears that...似乎……It happened that...碰巧……3)It + be +过去分词+从句It is said that...据说……It is known to all that...众所周知……It is reported that...据报道……It is believed that...据信……;人们相信……It is suggested that...有人建议……It must be pointed out that...必须指出……It has been proved that...已证明…….例如:It is believed that at least a score of buildings were damaged or destroyed.据信,至少有二十座楼房遭到破坏或彻底毁掉.It is suggested that the meeting should be put off.有人建议会议延期召开.It's reported that three people were killed in the accident and five were hurt badly.据报道,事故中三人丧生,五人重伤.It is known to all that Taiwan is an inseparable part of China.众所周知,台湾是中国不可分割的一部分.[巩固练习]1. Does _______ matter if he can't finish the job on timeA. thisB. thatC. heD. it2. It worried her a bit _______ her hair was turning grey.A. whichB. thatC. ifD. for3. _______ is a fact that English is being accepted as an international language.A. ThereB. ThisC. ThatD. It二、学习主语从句应该注意的几个问题1)引导词that与whatwhat既有引导主语从句的作用,同时又在从句中作句子成分(主语、宾语、表语等).这时what相当于all that/everything that...,常译成"所……的(东西、事情、话等.)";而that只起连接作用,本身无实际意义,在从句中也不担当任何句子成分.但that引导的主语从句放在句首时,不能省略that.例如:What is done can't be undone. (谚语)已成定局,无可挽回.What we can't get seems better than what we have.我们得不到的东西似乎比已得到的要好.That we should work out a plan to deal with the present serious situation is important.我们应该制定一项计划来应付目前严峻的形势,这一点非常重要.That a new teacher will come to teach us geography is true.一位新老师将来教我们地理,这是真的.[巩固练习]4. _______ what they told me really trueA. HasB. IsC. DoesD. Have5. It matters little _______ a man dies, but _______ matters much is _______ he lives.A. how; what; howB. how; it; howC. why; it; whyD. that; what; that6. _______ she couldn't understand was _______ fewer and fewer students showed interest in her lessons.A. What; whyB. That; whatC. What; becauseD. Why; that7. It is pretty well understood _______ controls the flow of carbon dioxide in and out the atmosphere today.A. thatB. whenC. whatD. how8. _______ fashion differs from country to country may reflect the cultural differences from one aspect.A. WhatB. ThatC. ThisD. Which9. -What made her parents so angry- _______ she had failed in the examination.A. AsB. BecauseC. SinceD. That2)引导词if和whetherif和whether引导动词后的宾语从句时一般可通用,但介词后的宾语从句、主语从句(放在句首时)、表语从句常由whether引导.例如:Whether she will go home or not is unknown.她是否回家还不得而知.Whether we shall raise ducks or geese remains to be decided.我们是养鸭还是养鹅仍没决定.=It remains to be decided whether/if we shall raise ducks or geese.但我们不能说If we shall raise ducks or geese remains to be decided.[巩固练习]10. _______ we'll go camping tomorrow depends on the weather.A. IfB. WhetherC. ThatD. Where3)其它引导词连接代词who, which, whom, whose有各自的意义,起连接作用,并在从句中充当语、宾语、表语、定语等;连接副词when,where, why, how等有各自的意义,起连接作用,并在从句中充当状语.[巩固练习]11. -Do you remember _______ he came-Yes, I do. He came by car.A. howB. whenC. thatD. if12. It was a matter of _______ would take the position.A. whoB. whoseC. whomD. whomever13. -I drove to Zhuhai for the air show last week.-Is that _______ you had a few days offA. whyB. whenC. whatD. where14. I read about it in some book or other, does it matter _______ it wasA. whereB. whatC. howD. which三、语气在It is necessary / natural / important / strange...+ that-clause这类句型里,that所引导的主语从句中谓语动词用"should +原形",表虚似语气.例如:It is necessary that the problem should be settled at once.这个问题必须马上解决.It's strange that he should have gone away without telling us.他竟然没向我们说一声就走了,真是奇怪.[巩固练习]15. It is necessary that a college student _______ at least a foreign language.A. mastersB. should masterC. masteredD. will master四、以it作形式主语的主语从句与强调句型的区别"It be + adj./n. + that-clause"与强调句型均有It be...that...之类的语言标志,但不同的是:①前者中的that 从句是主语从句.若删掉其中的It be和that,则剩余部分不论结构还是语意都不能成为一个句子;但若将后者中的It be和that去掉,则剩余部分的结构和语意仍能构成一个完整的句子.②强调句型译为汉语时可加上"正是……"或"就是……"之类的字眼,而主语从句则不可以.请比较下面两个句子:It is surprising that Mary should have won first place.令人惊奇的是玛莉竟然获得了第一名.It is Mary that has won first place.正是玛莉得了第一名.第一句话中的It是形式主语,that引导的是主语从句.句中的It is和that无法删除,一旦删除句子就不成立.第二句是强调句型,其中的It is和that可以去掉,因为没有It is和that句子仍然很通顺.Key: 1-5 DBDBA 6-10 ACBDB 11-15 AAADB表语从句1 The traditional view is ____ we sleep because our brain is “programmed”to make us do so. (2007上海)A. whenB. whyC. whetherD. that［答案］ D［解析］下划线处之后是包含一个原因状语从句的表语从句，如果看不出它是充当整个句子结构的表语从句将难以把握整个句子的意思。