it的用法很多，本文主要讲解它的基本用法、形式主语和形式宾语的用法以及强调句中的用法。
1. 用作人称代词，指代上文提到的事物、动物、性别不明或没必要知道性别的人。如：
“Where's your car?”
“It's in the garage.”
Her dog was howling at the door, so she let it in.
The baby next door kept me awake. It cried all night.
2. 用作非人称代词，用来指代时间、日期、地点、天气、温度、距离、环境、情况等。如：
It was 4 o'clock and the mail still hadn't come.
It's quite warm at the moment.
It's over 200 miles from London to Manchester.
It's getting very competitive in the car industry.
3. 用作形式主语，真正的主语常为不定式（短语）、动词-ing形式（短语）或名词性从句。如：
It's impossible for us to get there in time.
It's always sad saying goodbye to someone you love.
It's strange that she never mentioned the wedding.
4. 用作形式宾语，真正的宾语常为不定式（短语）、动词-ing形式（短语）或名词性从句。如：
Many people find it hard to stop smoking.
She finds it boring staying / to stay at home.
I find it strange that she doesn't want to travel.
【辨析】 it, one和that
1. it指物时，是明确指上文提到的那个事物。it可以代替单数可数名词、不可数名词及前面提到的事情或情况。如：
I can't find my ticket. I think I must have lost it. (it = my ticket)
2. one指前面的名词或名词短语所表示的同类事物中的一个，而不是指同一个事或物。one既可以代替人，也可以代替物，但只能代替可数名词，其复数形式为ones。如：
The train was crowded so we decided to catch a later one.
Those shoes are too small. We must buy some new ones.
3. that可以代替“the +单数可数名词或不可数名词”，用于特指。that不能代替人，不可带前置定语，但可带后置定语。如：
Are you sure the population of Shanghai is larger than that of Beijing?
The milk here is tastier than that of other places.
【即学即练1】根据括号内的汉语提示补全下面对话。
Alex: 1. _________________________ (现在几点)?
Nora: 7 p.m.
Alex: What about going for a walk?
Nora: I wanted to, but 2. _________________________ (外面在下雨). Shall we watch TV together?
Alex: Sure. Where is the remote control?
Nora: I 3. _________________________ (把它放在抽屉里了) last night. Ah-ha, here it is! Which channel do you want to watch?
Alex: I read in the newspaper that there's an interesting documentary on Channel 4 tonight.
Nora: OK. ... Interesting indeed. But 4. _________________________ (有这么多广告很烦人) during the interval. (The doorbell rang.) Someone is ringing the doorbell. 5. _________________________ (去看看是谁).
Alex: OK.
(Alex opens the door and finds his neighbour Rose standing outside.)
Rose: Sorry to disturb you, but would you please turn down the TV a little bit? I 6. _________________________ (发现难以集中注意力到我的学习上).
Alex: Sorry! We will turn down the TV at once.
Rose: Thanks.
it在强调句型中的用法。
【语境展示】 观察下面几组句子中it的用法，然后加以总结。
1. a. It was cholera that killed him.
b. It was Iris that / who found him there.
c. It's Lawrence that / who / whom you should be talking to.
d. It was three weeks later that he heard the news.
e. It was in New Zealand that Elizabeth first met Mr. Cronje.
2. a. Was it in this year that the war broke out?
b. Is it Tracy that / who / whom you are looking for?
3. a. Why is it that everyone thinks he is selfish?
b. What was it that they fought for?
4. a. It was because I wanted to buy a dictionary that I went to town yesterday.
b. It is what he said just now that makes me angry.
5. a. It must be your mother that / who / whom you are thinking of.
b. It might be my two sisters that / who know her best.
6. a. It is not until the end of the year that the traffic laws will take effect.
b. It was not until he was thirty that he started to paint.
【自我归纳】
1. it用在强调句中，可以对句子中除谓语以外的成分加以强调。强调句型的基本结构是：It is / was +被强调部分+ that / who / whom +句子的其余部分，被强调部分指人时，用who（强调宾语也可用whom）或that，指事物时用________（第1组例句）。
2. 强调句型的一般疑问句形式是：Is / Was it +被强调部分+ that / who / whom +句子的其余部分（第2组例句）。
3. 强调句型的特殊疑问句形式是：________ + is / was it that +句子的其余部分（第3组例句）。
4. 强调句型也可强调状语从句、名词性从句等（第4组例句）。
5. 在强调结构中，be前可使用表示推测的情态动词（第5组例句）。
6. not ... until 句型的强调句的形式是：It is / was not until +被强调部分+ that +句子的其余部分（第6组例句）。
【即学即练2】
I. 将下面句子改写为强调句（对画线部分内容进行强调）。
1. He bought a new coat for me.
________________________________
2. The Prime Minister is visiting Japan at the moment.
________________________________
3. The first attack started just after midnight.
_______________________________
4. Wendy had hidden the box under her bed.
______________________________
5. The telephone rang when she was about to go to bed.
_______________________________
6. I did not realize what had happened until the next day.
_______________________________
II. 根据提示改写下面句子。
1. It was the price that he was surprised at. （改写为一般疑问句）
______________________________
2. It is Mary who has won first place. （改写为一般疑问句）
______________________________
3. It was in Shanghai that I first met Philip. （对画线部分提问）
______________________________
4. It is Tom who has painted the windows green. （对画线部分提问）
______________________________
答案
【即学即练1】
1. What time is it now 2. it's raining outside 3. put it in the drawer
4. it's very annoying to have so many ads 5. Go and see who it is
6. find it hard to concentrate on my studies
【自我归纳】that；疑问词
【即学即练2】
I.
1. It was a new coat that he bought for me.
2. It is the Prime Minister that / who is visiting Japan at the moment.
3. It was just after midnight that the first attack started.
4. It was under her bed that Wendy had hidden the box.
5. It was when she was about to go to bed that the telephone rang.
6. It was not until the next day that I realized what had happened.
II.
1. Was it the price that he was surprised at?
2. Is it Mary who / that has won first place?
3. Where was it that you first met Philip?
4. Who is it that has painted the windows green?
