2011届高考英语一轮复习讲解：it的用法【知识要点】It的用法（一）作人称代词1、it代替前面（或后面）的单数名词或分句等所表示的事物。
e.g. You cannot eat your cake but have it.（it代替前面的cake）Although we cannot see it, there is air all around us. （it代替后面的air）They say he has left town, but I don’t believe it.（it代替前面They…town分句中的情况）2、代替有生命但不能或不必分阴阳性的东西（包括婴儿）。
e.g. Yesterday we saw a big tree. It was fully twenty metres high. （it代替前面的tree）The baby cried because it was hungry. （it代替前面的baby）3、在某些习惯说法中，可以代替人。
e.g. ---- Someone is knocking at the door, Peter. ---- Who is it? ---- It’s me.---- Who are singing? ---- It is the children.---- The light is still on in the lab. It must be the third-year students doing the experiment.4、it与one的区别：这两个词都可以代表前面说过的名词，但it用于同名同物的场合；one则用于同名异物的场合。
e.g. ---- Do you still have the bicycle? ---- No, I have sold it.---- Is this knife yours? ---- No. It is Xiao Zhang’s. Mine is the one on the desk.5、it与that的区别：两词都可代替某一特定名词，但that指同一类，并非同一个。
e.g. The climate of South China is mild（温和的）; I like it very much.（it指the climate of South China）The climate of South China is much better than that of Japan.（that指the climate）（二）作无人称代词it作无人称代词时，除了句中找不到它所代表的词语外，另一个特点是它后面的内容都是表示天气、时间、距离、度量衡及情况等。
It is fine (rainy, windy, etc.).It is noon.It is a half hour’s walk to the f actory.It is eighteen square metres in area.What does it matter?（三）作强调词，构成强调结构用以帮助改变句子结构，使句子的某一成分受到强调。
“It is (was) + 所强调的成分+ that (who) + 其它成分。
”在这个句型中，it本身没有词义。
注意: 在强调结构中，如被强调部分为时间状语或地点状语，其后的连接词也绝不能为when 或where，而应用that 。
在复习中，一定要注意句式的不同。
It was in Shanghai that I bought the guitar．(that引起强调句)It was Shanghai where I bought the guitar．(where引起定从)[来源:学§科§网]It was twelve o'clock when we arrived there．(when引起时间状语从句）It was at twelve o'clock that we arrived there．（that 引起强调句）（四）引导词it作形式主语（宾语）为了使句子平衡，常采用形式主语（或宾语）it ，而把真正的主语（或宾语）置于句子后面。
通常引导词it与它所代替的句子成分中间要夹有某些词。
e.g. It takes half an hour to go there on foot.（It与to go there on foot之间夹有takes half an hour四个词）We thought it strange that Mr Smith did not come last night. （it与that从句中间夹有strange）[来源:学&科&网][来源:学。
科。
网]但有时it与所替代部分之间并不夹有其它词。
e.g. You may depend on it that they will support you.（因为介词on之后一般不直接接that引导的宾语从句。
注意：it不是多余的，不能当作错句）（五）. it，one，that 的区别：作为代词，这三个词的对比使用是高考的热点之一。
---Why don't we take a little break? ---Didn't we just have __________?A．it B．that C．one D．thisThe Parkers bought a new house but _________will need a lot of work before they can move in．A．they B．it C．one D．whichone 用以指代同类事物中的任一，that 特指性强，指代可数与不可数词，而it指代上文提过的同一事物。
一、代词it用法例句代替前文提到过的东西或事情，用作人称代词。
This is a new dictionary. I bought it yesterday.这是一本新词学科网典，我昨天买的。
Tom joined the army last mouth. Do you know about it? 汤姆上月入伍了，你知道这事吗？代替指示代词，起着this或that的作用Is this your car? No, it isn’t. 这是你的汽车吗？不是。
What’s that?—It’s a video. 那是什么？它是一台录像机。
Whose room is this?—It is theirs.这是谁的房间，是他们的。
指明某人或某物的身分，还可指不明性别的婴儿Who’s there? It’s me. (It’s John) 谁在那儿？是我。
（是约翰）Go and see who it is that rings. It’s Bill.去看看是谁来的电话，是比尔。
The Greens have a new baby. It’s lovely.格林家有一个新生婴儿。
它很可爱。
指时间，距离，自然现象（天气，气候，明暗）量度，价值等It’s Sunday today. 今天是星期天。
It’s three months since he came here.自从他来到这里，已经三个月了。
How far is it to the Great Wall .到长城有多远？It’s getting dark. 天快黑了。
—How much is the coat? —It’s ninety dollars. 这件衣服多少钱？九十美元。
二、引导词it用法例句[来源:Z xxk. Com ][来源:学*科*网Z*X *X*代替不定式短语It is up to you to decide. 这事要由你决定。
It makes me happy to hear you have recovered.听说你恢复了健康，这使我很高兴。
代替动名词短语It’s no good smoking. 吸烟没有好处。
It’s worthwhile working the whole night on the problem.用整夜的时间来研究那个问题是值得的。
代替主语从句It doesn’t matter what you do. 你干什么都没有关系。
It seems that everyone has known the news.好象大家都知道这个消息。
用法例句K]形式[来源:Zxxk.Com][来源:Z_xx_k.Com]主语形式宾语代替不定式短语I consider it better to be early.我认为能够早一些更好。
We found it impossible to get there before July .我们觉得，要在七月以前到达那里是不可能的。
代替动名词短语We thought it no use doing that.我们认为做那事没有用。
代替宾语从句The teacher makes it clear that everyone should hand in his homework ontime .老师清楚地指出，每个人都应该按时交作业。
三、it在强调结构中强调句型：It is (was) +被强调部分+ that (who) + 其它强调例句说明部分主语It is I who am to blame. 是我该受责怪。
It w as your uncle that (who) came yesterday.昨天来的是你叔叔。
原句的谓语动词如果是现在或将来时态用It is …that(who)如果原句谓语动词是过去时态，则用It was…that(who)。
在宾语It was a new pen that Mother gave me .母亲给我的是一支新钢笔。
强调时间，地点，原因或方式时不要用when, where, how, 必须用that。
地点It was in the classroom that I left my umbrella.我把雨伞就落在了教室里。
状语时间It is at eleven that the train leaves.火车是在十一点钟离开。
方式It was just as he ordered that I acted.我正是照他吩咐的那样做的。
原因It was because he was in trouble that I tried my best to help him.正是因为他处境困难我才尽力帮助他。
宾补It was red that we painted the gate.我们把门油漆成红的颜色。