我们都知道it 可以指代非人称的它，所以it 它不是人，那么在这一单元，我们要向大家介绍一下这个“不是人”的it。
it 在句子中可作主语，it 在句子中作主语可起到以下作用。
（1）代替刚提到过的一件事。在这种情况下，it 可以指一个具体的东西（a），也可以指前面所谈的事情或情况（b）。
a.What is this？
这是什么？
It is a computer.
这是电脑。
b.You promised to write the article， you must do it.
你答应写这篇文章的，一定得写。
（2）起指示代词的作用，指一个人或事物。在这种情况下，it 所指的东西不是很具体，有时指做某个动作的人（a），有时指引起某种情况的事物（b）。
a.Who is knocking at the door？
谁在敲门？
It is Lily.
是莉莉。
b.It is the wind shaking the window.
是风刮得窗户响。
（3）表示时间、天气、距离、环境情况等。在这种情况下，it不指某个特别的东西，而是指以下几种情况。
① 自然现象。例如：
It is rather windy today.
今天风挺大。
It is drizzling (pouring， snowing hard).
现在正在下毛毛雨（下倾盆大雨、下大雪）。
It is fine (rather chilly， extremely hot) today.
今天天晴（有些冷、非常热）。
② 季节时间等。例如：
It was late autumn (early spring， mid-summer).
这时是深秋季节（早春季节、仲夏季节）。
It was twilight (midnight， ten o"clock in the morning).
这是黄昏时分（午夜、上午十点钟）。
③ 距离。例如：
It is about a night"s journey to the place by train.
到那个地方乘火车要一夜。
It is just one more stop to Toronto.
再停一站就到多伦多了。
④ 环境情况等。例如：
It was very quiet at the moment.
这时候很安静。
It will be lovely in the park today.
今天公园里一定很好玩。
（4）改变一个句子的结构，强调这个句子中的某一成分。在这种情况下，it 可以说没有意思，它只帮助改变一个句子的结构，使某一成分得到强调。例如：
It is medicine that counts.
起作用的是药物。
比如说“Xiao Yang met your sister in the zoo yesterday.”这个句子就可借助it改为下面几种形式，各强调一个不同的成分。
It was Xiao Yang who（或that）met your sister in the zoo yesterday.
是小杨昨天在动物园碰到你妹妹的。
It was your sister that（或whom）Xiao Yang met in the zoo yesterday.
小杨昨天在动物园碰到的是你妹妹。
It was in the zoo that（不用where）Xiao Yang met your sister yesterday.
小杨昨天是在动物园碰到你妹妹的。
It was yesterday that（不用when）Xiao Yang met your sister in the zoo.
小杨是昨天在动物园碰到你妹妹的。
改变结构的办法是：It+be+要强调的部分+that +（或who， which）+句子其他部分。比如：强调的部分指人时用who(m)，有时用that；其他情况多用that，间或用which；在口语中that 有时可以省略。
（5）代替一个由不定式、动名词短语或是从句表示的主语，使原来的这些主语可以放在句子后部，避免句子显得头重脚轻。在这种情况下，it 没有具体的意义，而只是帮助把真正的主语移到句子后面去，使句子显得平稳一些。能借助it 移到句子后面的主语有三种：一种由不定式表示，一种由动名词表示，一种由从句表示。
① 用不定式作主语的这类句子很多。例如：
It is funny of you to be still worrying about it.
你真可笑，还在为这事着急。
It is our duty to attend to this matter.
处理这事是我们的责任。
② 能以动名词作主语的这类句子比较少一些，主要在以 no good， no use， useless，senseless， nuisance， worthwhile， waste， dangerous 等词做表语的句子中用。例如：
It is no use talking to her about it.
和她谈这事没有用。
It is dangerous playing with fire.
玩火是危险的。
Is it worthwhile making such an experiment？
做这样的试验值得吗？
③ 能用从句作主语的带it 的结构常见的有下面几类：
a.It is a pity (shame， a fact， an honor， a wonder， a good thing， good news， no wonder …)
b.It is strange (natural， surprising， obvious， true， fortunate， good， and wonderful …)
c.It seems (happened， turned out， occurred to me， etc.) that …
d.It was said (reported， rumored， announced， arranged， decided， etc.) that ...
e.It is doubtful (not known， not decided， not made clear， to be found out， to be made clear， to be decided， etc.)+连接代词或副词引起的从句
f.It doesn"t matter (doesn"t make too much difference， doesn"t seem to matter much， doesn"t need to be bothered， doesn"t alter the situation， etc.) +连接代词或副词引起的从句
选择题。
1.- There is still a copy of the book in the library.Will you go and borrow ？
- No.I"d rather buy in the bookstore.
A.it；one
B.one；one
C.one；it
D.it；it
2.It is almost five years we saw each other last time.
A.before
B.since
C.after
D.when
3.It was some time we realized the truth.
A.when
B.until
C.since
D.before
4.How long do you think it will be China sends a manned spaceship to the moon？
Perhaps two or three years.
A.when
B.until
C.that
D.before
5.is our belief that improvements in health care will lead to a stronger， more prosperous economy.
A.As
B.That
C.This
D.It
6.He didn"t make clear when and where the meeting would be held.
A.this
B.that
C.it
D.these
7.As the busiest woman in Norton， she made her duty to look after all the other people"s affairs in that town.
A.this
B.that
C.one
D.it
8.I"d appreciate if you would like to teach me how to use the computer.
A.that
B.it
C.this
D.you
9.I just wonder that makes him so excited.
A.why it does
B.what he does
C.how it is
D.what it is
10.If I can help I don"t like working late into night.
A.so
B.that
C.it
D.them
11.- It"s been raining for a whole week.I think it"ll get fine soon.
- .We are getting into the rainy season now.
A.Yes， it will
B.Of course not
C.It"s possible
D.It"s hard to say
12.Someone is ringing the doorbell.Go and see who .
A.is it
B.he is
C.is he
D.it is
13.is a fact that English is being accepted as an international language.
A.There
B.This
C.That
D.It
14.I like in the autumn when the weather is clear and bright.
A.it
B.that
C.this
D.one
15.It was not until 1920 regular radio broadcast began to master a foreign language until without much memory work.
A.while
B.which
C.that
D.since
16.It was only when I read his poems recently I began to appreciate their beauty.
A.until
B.that
C.then
D.since
17.We will have to finish the job .
A.long it takes however
B.it takes however long
C.long however it takes
D.however long it takes
18.is known to everybody， the moon travels around the earth once every month.
A.It
B.As
C.That
D.What
19.no need for us to discuss the problem again since it has already been settled.
A.It has
B.There has
C.It is
D.There is
20.Bill"s aim is to inform the viewers that cigarette advertising on TV is illegal， ？
A.isn"t it
B.is it
C.isn"t he
D.is he
Fun Time（此处有音频学习资料）
Let It Be
顺其自然
When I find myself in times of trouble
Mother Mary comes to me
Speaking words of wisdom， let it be
And in my hour of darkness
She is standing right in front of me
Speaking words of wisdom， let it be
Let it be， let it be
Let it be， let it be
Whisper words of wisdom， let it be
And when the broken hearted people
Living in the world agree
There will be an answer， let it be
For though they may be parted
There is still a chance that they will see
There will be an answer， let it be
Let it be， let it be
Let it be， let it be
There will be an answer， let it be
Let it be， let it be
Let it be， let it be
Whisper words of wisdom， let it be
Let it be， let it be
Let it be， let it be
Whisper words of wisdom， let it be
And when the night is cloudy
There is still a light that shines on me
Shine until tomorrow， let it be
I wake up to the sound of music
Mother Mary comes to me
当我发现自己深陷困境
圣母玛利亚来到我身边
述说着智慧的话语，顺其自然
在我最黑暗的时刻
她就站在我面前
述说着智慧的话语，顺其自然
随他去，顺其自然
随他去，顺其自然
低语着智慧的话语，顺其自然
所有伤心的人们
生活在这个世界上
都将会有一个答案，顺其自然
即使他们被迫分离
他们仍有机会看到
都将会有一个答案，顺其自然
随他去，顺其自然
随他去，顺其自然
都将会有一个答案，顺其自然
随他去，顺其自然
随他去，顺其自然
低语着智慧的话语，顺其自然
顺其自然，顺其自然
顺其自然，顺其自然
低语着智慧的话语随他去
阴云密布的夜空
依旧有光照耀着我
直到明天，顺其自然
我被音乐之声唤醒
圣母玛利亚来到我身边
Speaking words of wisdom， let it be
Let it be， let it be
Let it be， let it be
There will be an answer， let it be
Let it be， let it be
Let it be， let it be
There will be an answer， let it be
Let it be， let it be
Let it be， let it be
Whisper words of wisdom， let it be
述说着智慧的话语，顺其自然
随他去，顺其自然
随他去，顺其自然
都将会有一个答案，顺其自然
随他去，顺其自然
随他去，顺其自然
都将会有一个答案，顺其自然
随他去，顺其自然
随他去，顺其自然
低语着智慧的话语，顺其自然