【知識點撥】
1.人稱代詞it，是第三人稱單數(shù)中性，代表前文已提到過的一件事物。如：
1）I love swimming. It keeps me fit. 我喜歡游泳，它能使我保持健康。
當說話者不清楚或無必要知道說話對象的性別時，也可用it來表示。 如：
2）It’s a lovely baby. Is it a boy or a girl? 寶寶真可愛，是男孩還是女孩？
2.指示代詞it，常用以指人。如：
1）Go and see who it is. 去看看是誰。
2）--- Who is making such a noise? -是誰發(fā)出這樣的吵鬧聲？
--- It must be the children. -一定是孩子們。
3.it無指代性，常用作沒有具體意義的主語，出現(xiàn)于表示天氣、氣候、溫度、時間、地點、距離等意義的句子中。如：
1）It is half past three now. 現(xiàn)在是三點半鐘。
2）It is six miles to the nearest hospital from here. 這里離最近的醫(yī)院也有六英里。
3）It was very cold; it snowed and grew dark. 天氣很冷；天下著雪，漸漸地變黑了。4.先行詞it.
it充當形式主語或形式賓語，本身無意義，只起一種先行引導(dǎo)的作用，先行詞不重讀。后面的真正主語或真正賓語通常是不定式結(jié)構(gòu)、-ing分詞結(jié)構(gòu)或名詞性從句。
（1）用作形式主語
1）It is difficult to translate this article. 翻譯這篇文章很難。
2）It is no use going there so early. 這么早去那里沒有用。
3）It is strange that he did not come at all. 真奇怪，他竟還沒來。
在上述諸例中，后置的真正主語可以取代先行it的位置，而出現(xiàn)于句首。
To translate this article is difficult.
Going there so early is no use.
That he did not come at all is strange.
（2）用作形式賓語
1）I found it difficult to explain to him what happened.
2）He thought it no use going over the subject again.
3）They kept it quiet that he was dead. 他們對他的死保密。
4）We must make it clear to the public that something should be done to stop pollution.
5. it為引導(dǎo)詞的強調(diào)句型
它的結(jié)構(gòu)形式是：It+be的一定形式+中心成分+that-/who-從句。
使用該句型有以下幾點請注意：
�、購娬{(diào)句的謂語is或was永遠用單數(shù)，其中is既可強調(diào)現(xiàn)在的情況，也可強調(diào)過去的情況，was只能強調(diào)過去的情況。
例如：It was/is yesterday that I met your father in the street．
②不管被強調(diào)部分是哪種狀語，只能用that連接，不得使用where、when等連詞。
例如：It was in the street that I met your father yesterday．
�、郾粡娬{(diào)部分為人時，可用who(主格或賓格)和whom(賓格)代替that，用that也行。
例如：It was your father that/whom /who I met in the street yesterday．
It was I that/who met your father in the street yesterday．
④強調(diào)句中也要注意主謂一致、人稱一致和否定轉(zhuǎn)移的問題。
例如：It is they who are our friends．（be）
It was until ten o'clock that we got home last night．(添加not)
�、葑⒁獠灰煜龔娬{(diào)句和其他從句。It is was…that…為強調(diào)句標志.
比較：It was ten o'clock when we got home last night．我們昨晚到家時已十點了。
It was at ten o'clock that we got home last night．我們昨晚是在十點到家的。
【知識過關(guān)】it用法演練
Task1 單項選擇(32分)
1.It took us over an hour ________ along the street.
A. walk B. to walk C. walking D. walked
2.I think it a great honour _______ to visit your country.
A. to invite B. inviting C. having invited D. to be invited
3.Many people now make_______ a rule to buy cards for their friends before Christmas.
A. themselves B. it C. that D. this
4. ________ is very clear to everyone that he's round and tall like a tree.
A. This B. What C. That D. It
5.In the United States, bus travel doesn't cost much as train travel,________ ?
A. don't they B. does it C. do they D. doesn't it
6.Someone is at the door, who is_______ ?
A. this B. that C. it D. he
7.-It is raining cats and dogs.
- ____________. .
A. So it is B. So is it C. Neither it is D. Neither is it
8.-My home is in that tall building over there.
- __________ ?
A. Can it see B. Can see it C. Can be seen it D. Can it be seen
9. _________ raining hard for 3 hours without stopping.
A. It is B. It was C. It has been D. It had been
10.-Has the boy got his bicycle now?
-Yes, the police gave_________. .
A. him to him B. it to it C. it to him D. him to it
11.-Boy, ____________.
-It is, looks like spring is coming soon.
-Yeh, It'll just be a few more weeks.
A. it's really a nice day today, isn't it?
B. what knid of weather are we going to have today?
C. do you think it is going to rain today?
D. what' it like outside today?
12.It is important ________ their offer.
A. reject B. rejects C. to reject D. rejecting
13.Has ________ been decided when we are to hold the sports-meeting?
A. that B. this C. it D. what
14.-Did Li Lei call me while I was out?
-Yes, it was ________ that called you.
A. him B. he C. who D. whom
15.Nothing is wrong with the radio _________ ?
A. isn't it B. is that C. is it D. isn't that
16.I don't know ________ makes her afraid of having her business discussed.
A. what it is about Mary that
B. that is it abut Mary what
C. what is it about Mary that
D. that is about Mary what
17.Which sentence is wrong?
A.I felt it impossible for him to take the exam.
B.I found it impossible that he might take the exam.
C.I thought that he might not take the exam.
D.In my opinion he might take the exam.
18.I don't think _____difficult for a Chinese student to master a foreign language within five years
A. that B. it C. too D. very
19.It's the second time you _______ late this week.
A. arrive B. arrived C. have arrived D. had arrived
20.It will not be_______ we meet again.
A. long before B. before long
C. soon after D. shortly after
Task2．用it開頭改寫句子(14分)
1. Her sisters offered to pay her fare.That was generous of them.
2.Her brother invited her to stay. That was very kind of him.
3.You found your wallet. That is lucky.
4.You couldn't find a less expensive hotel. That is a pity.
5.To walk in the garden is pleasant.
6.To pronounce a long word is often difficult.
7.To learn a foreign language is very important.
KEY:
Task1．
1.B 2.D 3.B 4.D 5.B 6.C 7.A 8.D 9.C 10.C
11.A 12.C 13.C 14.B 15.C 16.A 17.C 18.B 19.C 20.A
Task2．
1.It was generous of them (her sisters) to offer to pay her fare.
2.It was kind of her brother to invite her to stay.
3.It is lucky that you found your wallet.
4.It is a pity that you couldn't find a less expensive hotel.
5.It is pleasant to walk in the garden.
6.It is often difficult to pronounce a long word.
7.It is very important to learn a foreign language.