1、Unit 3A healthy lifeSection Grammarit的用法()一、it用作代词1it用作人称代词：(1)指代前面的名词或前面提到过的事；(2)指代性别不明的child或baby；(3)指代未出场的身份不明确的人。如：My friend offered me a beautiful gift yesterday, and I like it very much.我朋友昨天给了我一件漂亮的礼物，我非常喜欢。His sister has given birth to a baby recently. It is said it is very beautiful.他姐姐最近生了
2、个孩子。据说孩子很漂亮。Who is waiting for you at the bus stop?I have no idea. It may be my brother.“谁正在公共汽车站等你？”“我不知道。可能是我哥哥。”2it用作非人称代词：(1)it可以表示天气、时间、距离、自然现象、环境情况等；(2)it也可以表示一般的、笼统的情况。如：It is a fine day today, isnt it?今天是个好天气，对吧？It is five kilometres to the town from the village.从村庄到城镇有5千米的路。Its ten oclock n
3、ow.现在10点钟了。It is too bad. There is much work for me to do today.糟透了。今天我有太多的工作要做。3it可以指代指示代词this, that或不定代词something, nothing。如：Whenever she sees something that she likes, she goes and buys it.每当她看到了喜欢的东西，她就会去买下来。二、it用作引导词1it在句中作形式主语：it作为形式主语常用于下面句型中：(1)It beadj.(for sb.) to do.(对某人来说)做是的。(常用于此句型的形容词
4、有possible, necessary, important, easy, strange, natural等)(2)It ben.doing.做是的。(常用于本句型的名词有good, use等)(3)It beadj.doing.做是的。(常用于本句型的形容词有useless, worthwhile等)(4)It beadj.that.(对某人来说)做是的。(常用于此句型的形容词有necessary, important, strange, natural等)注意：此句型中从句一般用虚拟语气，即(should) do。(5)It be过去分词that.据。(常用于本句型的过去分词有said
5、, announced, believed, reported, known, hoped等)(6)It ben.that.做是的。(常用于此句型的名词有pity, honour, shame, wonder等) 如：It is impossible to get there by boat.坐船不可能到那里。It is no use giving him some advice.It is useless giving him some advice.给他提建议没用。It is necessary that the work should be done well.这项工作应该被完美完成，这
6、是必要的。It was said that the typhoon, Haiyan, had caused a lot of damage.据说台风海燕已造成了很大的破坏。Its a pity that you cant come.你不能来真遗憾。2it在句中作形式宾语：it作为形式宾语常用于句型“动词it形容词/名词/动词ing(for sb.) to do/that从句”中。常用动词有think, believe, suppose, consider, feel, make, keep等。如：They considered it important to have the work don
7、e on time.他们认为按时完成这项工作很重要。We make it a rule to visit the old every weekend.我们规定每个周末都去拜访那些老人。He thought it no use trying to convince them.他认为说服他们没有用。I think it important that you (should) attend the conference.我认为你去参加这个会议很重要。3it的其他句型：(1)It remains to be done从句(真正的主语)有待于如：It remains to be seen whether
8、 making a trip often does good to the old couples health.经常旅行是否对老年夫妇的健康有好处有待于证实。(2)Ithits/strikes/occurs to sb.从句(真正的主语)，某人突然想起 如：It occurred to me that we should start off at once.我突然想起我们应该立刻出发。(3)动词appreciate/hate/love/like/dislike后面由if或when引导从句时，中间用it，构成“appreciate/hate/love/like/dislikeitif/when
9、从句”。如：He will appreciate it if they invite him.如果他们邀请他，他将非常感激。She hated it when he bragged that he was the most important.她讨厌他自吹自己最重要。(4)动词短语rely/depend on/upon(依靠)，see to(负责，照料)，answer for(负担，担保)，ask for(请求)后跟that引导的从句作宾语时，中间需用形式宾语it，构成“动词短语itthat从句”结构。如：You can depend on it that she is always conc
10、erned about her own interests.她总是关心自身的利益，对这一点可以打包票。Please see to it that the door is locked.请确保门锁了。(5)用于“动词it介词短语that从句”结构中：take it for granted that.认为理所当然owe it to sb.that.把归功于某人leave it to sb.that.把留给某人keep it in mind that.把记在心里如：He owes it to his doctors care that he is quite well again.多亏医生的照料，他
11、的病才好了。Keep it in mind that you have to be home by 11 oclock.记住，你必须在11点以前回家。.句型转换(用it作形式主语)1We all knew that they had broken their promise.It_was_known_that they had broken their promise.2If you want to give up smoking in a short time, it will be difficult.It_is_difficult_to_give_up smoking in a shor
12、t time.3Since you have spilt your milk, crying over it is useless.Its_useless/no_use crying over spilt milk.4He has made up his mind. You neednt try to persuade him.Its_not_necessary for you to try to persuade him.5The weak baby is becoming stronger and stronger, which makes his parents happy.It mak
13、es his parents happy that the weak baby is becoming stronger and stronger.单句语法填空1This house is beautiful with a garden. We really like it very much.2I have a new copy of the book. Id like to send it to you.No, thanks. Id rather buy one in the bookstore.3Id appreciate it if you would like to teach me
14、 how to use the computer.4The doctor thought it better for you to have a holiday than to keep on working.5It never occurred to me that you could succeed in persuading him to change his mind.6Someone is ringing the doorbell. Go and see who it is.7Its no use complaining (complain) without taking actio
15、n.8The soldiers feel it their duty to defend their motherland.9This is not my story, nor is it the whole story. My story plays out differently.10Well, you mustnt play on the road. It is dangerous!.句型训练1It_is_reported_that (据报道) there was a serious accident on that highway last weekend.2How_far_is_it (多远) from your hometown to Beijing?3Keep_it_in_mind_that (要牢记) you must finish your task by this weekend.4They_make_it_clear (他们表明) to the public that they are doing an important and necessary job.5New technologies have made_it_possible (使可能) to turn out new products faster and at lower costs.
