超详细的It的用法归纳总结（附习题及答案）
一、It是代词
指除人以外的一切生物和事物，用来指代时间、季节、天气距离、环境。在这里，i是一个虚词，没有任何实际意义。例如:
①It is a quarter to eight now.
现在是八点差一刻。
②It is midnight. 现在是午夜。
③It is time for breakfast.
现在是吃早饭的时间。
④-What is the date today?今天几月几号?
--It is December 3rd. 十二月三号。
⑤--What season is it?现在是什么季节?
--It is summer. 夏季。
⑥--What is the weather like today?
今天天气如何?
--It is fine.天气很好。
--It is foggy and wet.天气多雾又潮湿。
⑧How far is it from the bus station to your home? 从汽车站到你们家有多远?
⑨It is around five miles to the shopping center.从这儿到购物中心大约有五英里。
二、It用作主语
用来指代文中出现过的人或事。
it此时可用来代替一个名词，一个短语，一个从句或一个句子。在句中可指生物,非生物，不明性别的人，也可以指一个动作或件事情(人物型)，还可以指人或事物的身份(指示型)。在这里,it是有实际意义的。例如:
①--What is this?这是什么?
--It is a computer.这是一台计算机。
②--What is that?那是什么?
--It is a map.那是一张地图。
③--Where is the dog?狗在哪儿?
--It is lying under the tree.它在树下面躺着呢。
④--Where is the post office?邮局在哪儿?
--It is near the hospital 在小医院附近。
⑤--Who is that man?那个人是谁?
--It is my brother.是我哥哥。
⑥He tried to get rid of smoking，but it was impossible.他尝试着戒烟，但那是不可能的。
⑦If you exercise every day ,it will keep you well and strong.如果你每天锻炼，你就会变得健康。
三、It作形式主语
为了避免将句中作真主语的不定式、动名词和名词子句置于句首造成头重脚轻，习惯上it可作为形式主语置于句首，指代后面的真正主语，使句子显得流畅。it 作形式主语的句型有:
It+谓语+不定式
It+谓语+动名词
It+谓语+名词性从句
1.不定式具有名词的性质，在句子中可作主语。例如: It is wise to understand each other
=To understand each other is wise.
互相理解是明智的
记：把it翻译为中文时,it没有实际意义，要把后置的不定式作为主语来翻译。例如:
①It is necessary to have a good sleep before the test for us.
= To have a good sleep before the test for us is necessary.
对我们来说考试前好好睡一觉是很必要的。
②It is wrong to do so.=To do so is wrong.
这样做是错误的。
③It is a bad habit to eat junk food.
= To eat junk food is a bad habit.
吃垃圾食品是一种坏习惯。
④It took us 12 years to complete the project.
= To complete the project took us 12 years.完成这项工程花费了我们十二年的时间。
2.与不定式不同,动词-ing作主语时一般置于句子开端;置于句尾时则常将动词-ing改成不定式。因此用it代替动词-ing作形式主语的句子较少，主要用在以no use，useless, not any use, not much use, not any good, not much good, no good, no help, dangerous，senseless, worth ，while ,a waste 等词作主语补足语的句子中。例如:
①It is no use arguing with the people who won't see reason.和不讲理的人争论是无用处的。
②Is it any good( any use ) making such a decision?做这样一个结论有用吗?
③It is dangerous playing with fire. 玩火是危险的。
④It is worth reading the book.
读这本书值得一读。
四、It可代替由that、连接代词或连接副词引导的名词性从句。
①It was clear that he had desire for peace.
= That he had desire for peace was clear.
很清楚他有和解的愿望。
②It was reported that the new president had been elected.
= Thatthe new president had been elected was reported.
据报道新总统已被选出来了。
③It is a pity that her sister cannot go shopping with us.
= That her sister cannot go skating with us is a pity.
她的姐姐不能和我们一起去购物,这太令人遗憾了。
五、It +名词性从句的结构一般可归为六类。
1.It+be动词+形容词+that从句
①It is strange/ obvious natural good/ possible/ funny/ surprising/usual +that从句。例如:
②It is strange that nobody knows where he lives.奇怪的是，谁也不知道他住在哪里。
