1、It 最基本的用法是最基本的用法是，主要代表刚提到的东西以避免重复。，主要代表刚提到的东西以避免重复。Look at that car.Its going much too fast.Where is the car key?-I put it in your drawer.也可以代表抽象的东西。也可以代表抽象的东西。Its all my fault.也可以指动物或未知性别的婴儿。也可以指动物或未知性别的婴儿。What a beautiful baby，is it a boy?How about the baby?-Ill take care of it.还可代表一个彼此都知其何所指的东西。还
2、可代表一个彼此都知其何所指的东西。Where does it hurt?If he doesnt come,I cant help it.You have saved my life.I shall never forget it.It 可以表示可以表示“是谁（在某处或做某事）是谁（在某处或做某事）“Whos that?”“Its me.”Its your mother on the phone.“Why,its you!”she cried.It还可以用来泛指某件事还可以用来泛指某件事Isnt it awful!It doesnt matter.it 有时并不指具体东西，而指天气、时间、环境
3、、距离等，有时并不指具体东西，而指天气、时间、环境、距离等，称为非人称代词称为非人称代词it.Its raining.Its Tuesday today.Its quiet here.Its two miles to the beach.非人称代词非人称代词it：It 用于代替指示代词：用于代替指示代词：替代词替代词one,ones,that,those,it,this,that1)one,ones,that,thoseThat替换单数可数名词或不可数名词；替换单数可数名词或不可数名词；one只替换单数的可数名词。只替换单数的可数名词。The vase on the left is more
4、beautiful than the one on the right.The coffee produced in Brazil is more famous than that in Mexico.That只用于替换表示事物的名词，只用于替换表示事物的名词，而而one/ones替换表示人和表示替换表示人和表示事物的名词皆可。事物的名词皆可。His younger sister is taller than the elder one.I need the plastic bags,not the paper ones.The computers in our school are conn
5、ected to the Internet while those in their school arent.The football players on our team seem to be more energetic than those on your team.That/those一般用于替换有定冠词的名词；一般用于替换有定冠词的名词；one/ones用于替换有用于替换有不定冠词的名词。不定冠词的名词。The style of the building is similar to that of a temple.A CD player made in Japan costs
6、more than one made in Hong Kong.That/those一般不带前置定语，但必须有后置定语。一般不带前置定语，但必须有后置定语。One/ones都可。当替换词的后置定语用所有格的都可。当替换词的后置定语用所有格的of短语或当替换词被短语或当替换词被所有格修饰时，不用所有格修饰时，不用one/ones而用而用that of/those of.I like the vase better than the one/that in another shop.The windows of your flat are cleaner than those of mine.A
7、grandparents job is easier than that of a parent.2)it,this 和和 that都可以替代前文已提到的事或情况，细微差别在于都可以替代前文已提到的事或情况，细微差别在于it不如其余不如其余两者那么强调。两者那么强调。So she decided to paint the door pink.It upset the neighbours a bit.So she decided to paint the house pink.That really upset the neighbours,as you can imagine.当前面提到的事
8、物不止一件时，当前面提到的事物不止一件时，it通常指最先提到的事物，而通常指最先提到的事物，而This/that是指最后提到的事物。是指最后提到的事物。We keep the ice cream machine in the spare room.It is mainly used by the children.(指指 the machine)We keep the ice cream machine in the spare room.This/That is mainly used by the children.(指指the spare room)This可以出现在它所指代的事物之前；
9、而可以出现在它所指代的事物之前；而that则指上文所提到的则指上文所提到的事物。事物。Listen to this!We will have three days off.“A penny saved is a penny earned.”Who said that?3)It和和oneIt用以指特定的前面提到过的事物，即：用以指特定的前面提到过的事物，即：it和它替换的是同一个和它替换的是同一个事物，事物，it前无修饰语；而前无修饰语；而one用于替换与前提事物有共同之处用于替换与前提事物有共同之处但并不完全一样的事物，因此，但并不完全一样的事物，因此，one之前或之后一定有修饰语之前或之后一
10、定有修饰语来加以区别。来加以区别。I bought a dictionary three years ago and I am still using it now.I bought a dictionary three years ago but I am going to buy a new one soon.形式主语形式主语it：有下面几种类型：有下面几种类型：be+形容词形容词+不定式不定式 eg:Its better to be early.be+名词名词+不定式不定式 eg:It was his duty to take care of the orphans.be+介词短语介词短
11、语+不定式不定式 eg:Its beyond me to say why.It+及物动词及物动词+宾语宾语+不定式不定式 eg:It makes me sick to think about it.be+名词名词+动名词动名词 eg:Its no good standing here in the cold.be+形容词形容词+动名词动名词 eg:Its helpless trying to convince her.其他结构其他结构+动名词动名词 eg:It doesnt matter waiting a few more days.用于由用于由that 引导的主语从句，有下面几种类型：引导
12、的主语从句，有下面几种类型：it+be+形容词形容词+that从句：从句：eg:It is natural that they should have different views.it+be+名词名词+that从句从句:eg:Its a shame that youre sick.it+动词（动词（+宾语）宾语）+that从句从句 eg:It happened that she wasnt in that day.Eg2:It never occurred to me that perhaps she was lying.It+动词的被动语态动词的被动语态(said/believed/th
13、ought/expected/reported/known+that从句从句 eg:Its said that there has been an earthquake in India.形式宾语形式宾语it:it 可以代表不定式：可以代表不定式：She found it difficult to convince him.He felt it his duty to take care of them.It 代表代表that引导的从句：引导的从句：I took it for granted(that)you would be coming.It代表连接代（副）词引导的从句：代表连接代（副）词
14、引导的从句：He hasnt made it clear when he is coming back.They havent made it known where the meeting is to take place.用用it跟从句用法：跟从句用法：1）it+be+形容词形容词+从句：从句：It is not clear to me why he behaved like that.2）it+be+名词名词+从句从句:Its a puzzle how life began.3）it+动词（动词（+宾语）宾语）+从句从句 It doesnt matter much where we li
15、ve.It makes no difference whether we go by train or by boat.4）it+动词的被动语态动词的被动语态+从句从句 It is not decided who will edit it.5）it+动词动词be+that从句从句 No,it couldnt be that they were interested in him.6）It+be+一点时间一点时间+when It was Christmas Eve when I got the news of his being killed in a car crash.7）It+be+一段时
16、间一段时间+since It is/has been three week since I last heard from him.8）It is time to do/that(谓语用过去时态）谓语用过去时态）It is time for us to give the house a thorough cleaning.It is time that we gave the house a thorough cleaning.9）It+be+the first/second time that(谓语动词用完成时态）谓语动词用完成时态）It is the first time in histo
17、ry that two Nobel Prizes have been awarded to the same person.10）It takes sb.Time to do It took Mary 20 minutes to choose a suitable dress for the party.Nancy saw your sister in Tokyo last week.It was Nancy who saw your sister in Tokyo last week.It was your sister whom Nancy saw in Tokyo last week.I
18、t was in Tokyo that Nancy saw your sister last week.It was last week that Nancy saw your sister in Tokyo.It 用于强调句用于强调句结构：结构：It+动词动词be+强调部分强调部分+who(whom)/that+其他部分其他部分it可以用来对句子的某一成分加以强调。可以用来对句子的某一成分加以强调。有些否定句也可以改成这种强调结构：有些否定句也可以改成这种强调结构：I didnt hear from her until last summer.It wasnt until last summ
19、er that I heard from her.I didnt do all this for myself.It wasnt for myself that I did all this.问句也可变成这种结构：问句也可变成这种结构：Who called him“comrade”?Who was it that called him“comrade”?How did you forget to lock the door?How was it that you forgot to lock the door?Ex:把下列句子改为强调句：把下列句子改为强调句：1.Peter saw his f
20、riend in the park yesterday.2.I didnt receive my letter until yesterday?4.Did it happen in 1980?5.Why does everyone think Im narrow-minded?1.Peter saw his friend in the park yesterday.It was Peter who saw his friend in the park yesterday.It was his friend whom Peter saw in the park yesterday.It was
21、in the park that Peter saw his friend yesterday.It was yesterday that Peter saw his friend in the park.2.I didnt receive my letter until yesterday?It wasnt until yesterday that I received my letter.4.Did it happen in 1980?Was it in 1980 that it happened?5.Why does everyone think Im narrow-minded?Why was it that everyone thinks Im narrow-minded?
