動詞不定式，動名詞或主語從句作主語時，通常把它們放在謂語動詞前，而用 it 作形 式主語，放到句首，常見句型有：

　　1. It + be + 形容詞 主語從句，如： 形容詞+主語從句 ，

　　It is uncertain whether he can come to Jenny’s birthday party or not.

　　It + be + 形容詞 + （for sb.）+ 動詞不定式 等作表語，

　　*這類句型常用形容詞 easy, difficult, hard, important, possible，wise 等，

　　*為了強調不定式動作的執行者， 為了強調不定式動作的執行者，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.

　　It + be + 形容詞 + (of sb.) + 動詞不定式，

　　*這類形容詞常是表示心理品質 性格特征的 如：kind, nice stupid, clever, foolish, polite, impolite, silly, selfish, considerate 等。

　　*某人和這些形容詞可以構成主系表結構。 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.

　　(3)It + be +名詞詞組 + 動詞不定式，

　　It is not a good habit to stay up too late.

　　2. It + be + 名詞詞組+ 主語從句，這類名詞有：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.

　　It + be + 過去分詞 + 主語從句，這類過去分詞有：announced, believed, expected, hoped, decided, reported, said, shown 等， 如：

　　It is reported that people were killed in the earthquake.

　　It is not decided who will give the operation to the patient.

　　4. It + 不及物動詞(seem, appear, happen 等) + 主語從句 這類不及物動詞有：appear,

　　happen, seem 等， 如：

　　It seemed that he didn’t tell the truth.

　　It happened that I was out when he called.

　　It + be + 名詞或形容詞 + 動名詞， 這類名詞和形容詞常常是： 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.

　　It + take ( sb. )+ 時間（金錢）+ 動詞不定式，如： 時間（金錢） 動詞不定式，

　　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.

　　實戰演練：

　　4. Is----------- necessary to take off our shoes when we enter the lab?

　　A. everyone 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 situation is hopeless now.

　　A. to go B. to be going C. going D. having 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’s life 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

　　1 ______ he will come is certain.

　　A What

　　B That

　　C Which

　　D As

　　2 ______ we need is more time.

　　A What B that C Why D Which

　　3 It is a pity ______ he can’t attend our meeting.

　　A what B that C which D As

　　4 It's hard to say ______ football team will win the match.

　　A what B which C why D that

　　5 _____ he did it is not known.

　　A Why B Which C What D That

　　6 My idea is ______ we should help her do housework.

　　A that B what C why D which

　　7 The question is _____ we can catch the early bus.

　　A if B whether C why D what

　　8 This is _____ he wanted.

　　A what B which C where D why

　　9 This is ______ she had a day off. A what B why C which D how

　　10 I think _______ it is necessary for her to finish the task.

　　A that B what C which D who

　　11 Hearing ______ her son was badly wounded, she hurried to the hospital.

　　A what B that C which D why

　　12 Our teacher suggested ______ we should try to make changes.

　　A what B that C which D why 13 Please tell me _____ is the first man to invent a car. A what B which C why D who

　　14 Show me ______ bus I should take to the city center.

　　A what B which C why D who

　　15 I don’t know ______old they are.

　　A what B how C why D who

　　16 The news _____China hosted the 2008 Olympic Games successfully is very encouraging.

　　A that B how C why D who

　　17 His absence due to the fact ______ he was seriously ill.

　　A how B which C that D what

　　18 The suggestion _______ we think it in another way raised a storm of objections.

　　A what B which C that D why

　　19 The idea ______ we should help the people in the earthquake-stricken areas is worth praising.

　　A that B what C why D how

　　20 He made a promise ______ anyone set him free he would make him very rich.

　　A that what B if C what D that if

　　三． 填空題 來填空。 用 what, how, which, when, where, why, whether 來填空。 1 _____ she will leave for Guangzhou is not known.

　　2 ______ I am going to say has nothing to do with music.

　　3 ______ one she will choose doesn’t matter much.

　　4 ______ they were carrying out the experiment has not been decided yet.

　　5 ______ Kevin is late for the concert is not clear.

　　6 ______ she will study medicine or computer needs to be discussed.

　　動詞不定式，動名詞或主語從句作主語時，通常把它們放在謂語動詞前，而用 it 作形 式主語，放到句首，常見句型有：

　　1. It + be + 形容詞 主語從句，如： 形容詞+主語從句 ，

　　It is uncertain whether he can come to Jenny’s birthday party or not.

　　It + be + 形容詞 + （for sb.）+ 動詞不定式 等作表語，

　　*這類句型常用形容詞 easy, difficult, hard, important, possible，wise 等，

　　*為了強調不定式動作的執行者， 為了強調不定式動作的執行者，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.

　　It + be + 形容詞 + (of sb.) + 動詞不定式，

　　*這類形容詞常是表示心理品質 性格特征的 如：kind, nice stupid, clever, foolish, polite, impolite, silly, selfish, considerate 等。

　　*某人和這些形容詞可以構成主系表結構。 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.

　　(3)It + be +名詞詞組 + 動詞不定式，

　　It is not a good habit to stay up too late.

　　2. It + be + 名詞詞組+ 主語從句，這類名詞有：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.

　　It + be + 過去分詞 + 主語從句，這類過去分詞有：announced, believed, expected, hoped, decided, reported, said, shown 等， 如：

　　It is reported that people were killed in the earthquake.

　　It is not decided who will give the operation to the patient.

　　4. It + 不及物動詞(seem, appear, happen 等) + 主語從句 這類不及物動詞有：appear,

　　happen, seem 等， 如：

　　It seemed that he didn’t tell the truth.

　　It happened that I was out when he called.

　　It + be + 名詞或形容詞 + 動名詞， 這類名詞和形容詞常常是： 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.

　　It + take ( sb. )+ 時間（金錢）+ 動詞不定式，如： 時間（金錢） 動詞不定式，

　　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.

　　實戰演練：

　　4. Is----------- necessary to take off our shoes when we enter the lab?

　　A. everyone 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 situation is hopeless now.

　　A. to go B. to be going C. going D. having 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’s life 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

　　1 ______ he will come is certain.

　　A What

　　B That

　　C Which

　　D As

　　2 ______ we need is more time.

　　A What B that C Why D Which

　　3 It is a pity ______ he can’t attend our meeting.

　　A what B that C which D As

　　4 It's hard to say ______ football team will win the match.

　　A what B which C why D that

　　5 _____ he did it is not known.

　　A Why B Which C What D That

　　6 My idea is ______ we should help her do housework.

　　A that B what C why D which

　　7 The question is _____ we can catch the early bus.

　　A if B whether C why D what

　　8 This is _____ he wanted.

　　A what B which C where D why

　　9 This is ______ she had a day off. A what B why C which D how

　　10 I think _______ it is necessary for her to finish the task.

　　A that B what C which D who

　　11 Hearing ______ her son was badly wounded, she hurried to the hospital.

　　A what B that C which D why

　　12 Our teacher suggested ______ we should try to make changes.

　　A what B that C which D why 13 Please tell me _____ is the first man to invent a car. A what B which C why D who

　　14 Show me ______ bus I should take to the city center.

　　A what B which C why D who

　　15 I don’t know ______old they are.

　　A what B how C why D who

　　16 The news _____China hosted the 2008 Olympic Games successfully is very encouraging.

　　A that B how C why D who

　　17 His absence due to the fact ______ he was seriously ill.

　　A how B which C that D what

　　18 The suggestion _______ we think it in another way raised a storm of objections.

　　A what B which C that D why

　　19 The idea ______ we should help the people in the earthquake-stricken areas is worth praising.

　　A that B what C why D how

　　20 He made a promise ______ anyone set him free he would make him very rich.

　　A that what B if C what D that if

　　三． 填空題 來填空。 用 what, how, which, when, where, why, whether 來填空。 1 _____ she will leave for Guangzhou is not known.

　　2 ______ I am going to say has nothing to do with music.

　　3 ______ one she will choose doesn’t matter much.

　　4 ______ they were carrying out the experiment has not been decided yet.

　　5 ______ Kevin is late for the concert is not clear.

　　6 ______ she will study medicine or computer needs to be discussed.