祈使句：
表示请求或命令的句子是祈使句。祈使句一般用降调，为使祈使句听起来比较婉转，可用低声调，祈使句句末用句号或感叹号。
每种类型又有肯定形式和 祈使句的组成
①动词原形+其他
②Please+动词原形+其他
③否定形式:don‘t+动词原形,用don’t否定时，只能用其缩略形式。
例如：
Welcome to Beijing Park. 
Walk about three blocks. 
Don’t mention it.

 

祈使句的含义：

1. 表请求 
Pass me the sugar, please. 请把糖递给我。

2. 表命令 
Put up your hands. 举手。 
Fill in this form. 把这个表填好。

3. 表建议 
Let’s have dinner together. 我们共进晚餐吧。

4. 表邀请 
Come in and have a seat. 进来请坐。 
Help yourself to some fruits. 请吃水果。

5. 表警告 
Hurry up or you will be late.抓紧点，不然你要迟到了。 
Do that again and you”ll be in trouble.要是再干那事，你会有麻烦的。

6. 表禁止 
Don’t touch the exhibits.不要触摸展品。 
Don’t play on the road.不要在马路上玩耍。

7. 表叮嘱             
Be sure to get there before nine. 务必在九点前赶到那里。 
Take care not to catch cold. 小心别着凉了。

8. 表号召 
Workers of all countries, unite! 全世界工人阶级联合起来！

9. 表祝愿 
Have a good trip. 祝你旅途愉快。

祈使句有三种类型：
一、含第二人称主语的祈使句
1. 当祈使的对象是第二人称you时称为含第二人称主语的祈使句。
这时，主语you通常不出现在句中，谓语动词用原形。
有时在句首或句末加please，还可加上称呼语，用逗号与句子主体隔开。如：
Please be quiet, boys! 孩子们，请安静！
Come this way, please. 请走这边。
如要加强语气，可在动词前加do。如：
Do keep away from the fire! 切记远离火种！
2. 否定式在谓语动词前加Don’t或Do not,强调否定式则在动词前加Never。如：
Don’t alway make the same mistake. 不要老犯同一个错误。
Never be late again. 千万别再迟到了。
3. 有时，为了强调指明向谁提出要求或发出命令，或表达说话人的急躁、厌烦、不满、恼怒的情绪，就用主语you表示，且放在动词前。如：
You come here! 你到这里来！
You mind your head! 小心别碰到头了！
若为否定式，则把Don’t放在主语you之前。如：
Don’t you come here! 你别来这里！

二、含第一、第三人称主语的祈使句
1. 含第一或第三人称主语的祈使句通常以Let开头，
第一人称由“Let + me / us +动词原形”构成，
第三人称由“Let + 第三人称代词（用宾格）或名词+动词原形”构成。
这类祈使句往往用于提出建议。如：
Let me have a try if you don’t want to. 如果你不想，就让我试一试吧。
Let’s spend this weekend in the country. 咱们到乡下去度这个周末吧。
Let him be here by ten o’clock. 叫他10点到这里吧。
有时也可以先称呼对方的名字，，后跟一句无人称主语的祈使句。如：
Jane, sit down please. 简，请坐下。
Mum, remember to bring me an umbrella. 妈妈，记得给我带把伞。
2. 这类祈使句的否定式是在动词原形前加not，也可以在let前加Don’t。如：
Let’s not wast our time about it. 我们不要为了这件事而浪费时间。
Don’t let us wait here. 别让我们在这儿等。
Don’t let him go out. 别让他出去。

三、无动词祈使句
在请求、命令和口号中，常用无动词祈使句，它实际上是省略了动词，从而使语句更简洁或有力。如：
Just a minute, please! 请稍等！
This way, please! 请这边走！
Attention! 立正！
Up the stairs! 上楼！
To the playground, everyone of you! 到操场上去，你们每个人都得去！
在一些指示牌上，常用“No +动名词/名词”构成简略式的否定祈使句。如：
No smoking! 禁止抽烟！
No parking! 禁止停车！
No photos! 禁止拍照！
还有一些是祝词类的无动词祈使句，如：
May　you　succeed！祝你成功！
Long　live　our　friendship！我们的友谊万岁！

祈使句特点口令：
祈使句无主语,　主语you常省去;
动词原形谓语当,　句首加don't否定变;
朗读应当用降调,　句末常标感叹号。

祈使句的语调特点 ：
1、语音强度一般比陈述句重，书面上用叹号表示。
2、句末用降调，较长句子的后半部分几个音节速度加快。

对特定的人使用的祈使句：
祈使句如Wait here! (在这儿等着!) 可以是对一个人说，也可以是对几个人说，其主语暗含you。
但我们却可以用下列方式引起我们说话的对象的注意：
■You+祈使语气动词
You wait here for a moment. 你在这儿等一会儿。
语调和重音很重要。在上面这一句里，如果不重读you，那么句子的意思是this is where you wait (这就是你应等着的地方)；
如果重读you，那么句子的意思就是this is what I want you to do (这是我要你做的事)。
此外，重读you时还可以表示愤怒、敌意或不客气。如：
You mind your own business! 不关你什么事
You try teaching 40 noisy children five days a week! 你来试试每周5天教40个吵闹的孩子!
在否定句中Don’t要重读 (不重读you)。如：
Don’t you speak to me like that! 你别这样跟我讲话!

■“you+人名”或“人名+you”
You wait here, Jim, and Mary, you wait there. 你等在这儿，吉姆；玛丽，你等在那儿。

■“祈使语气+人名”或“人名+祈使语气”：
Drink up your milk, Sally! 把你的牛奶喝光，萨利!
Sally, drink up your milk! 萨利，把你的牛奶喝光!

■祈使语气+反身代词
Enjoy yourself. 你好好享受吧。
Behave yourself. 你放规矩点。

■对一群人讲话时，祈使语气可与everybody, someone之类的词连用：
Everyone keep quiet! 大家安静!
Keep still everybody! 每个人都保持不动!
Nobody say a word! 都不许说话!
Somebody answer the phone please. 请来个人接电话。

■在表示否定的命令语气后面可用带any的复合词
Don’t say a word anybody! 谁都不要说话!
Don’t anybody say a word! 任何人都不许说话!

宾语从句：
在句子中起宾语作用的从句叫做宾语从句。
宾语从句分为三类：动词的宾语从句，介词的宾语从句和形容词的宾语从句。
宾语从句连接代词主要有：
who, whom ,whose ,what ,whoever ,whomever ,whosever, whatever, whichever 等。

宾语从句的特点:
1.宾语从句可以作及物动词、介词及形容词的宾语。
2.宾语从句的语序一律用陈述句语序。
3.连接词that引导宾语从句在句中无词义，不充当句子成份，多数情况下可以省略。
4.whether 和 if 都可引导宾语从句，但 whether后可紧跟or not；whether从句可作介词的宾语。
5.如果从句太长，可以用形式宾语it.

宾语从句的时态:
1.主句是一般现在时，从句根据实际情况使用任何时态。
例句：The headmaster hopes everything goes well.
2.主句是过去时态，从句须用过去时态的某种形式。
例句：She was sorry that she hadn’t finished her work on time.
3.当宾语从句表示的是一个客观真理或者事实时，即使主句是过去时，从句也用一般现在时态。
例句：The teacher told his class that light travels faster than sound.
4. 如果从句的动作发生在主句之前，则从句要用过去完成时态。 

宾语从句的语序:
A. 宾语从句必须用陈述语序。 　　
False: He is wondering when can he finish this difficult job. 　　
Right: He is wondering when he can finish this difficult job.
B. 有时候可以用it 作形式宾语，而把真正的宾语从句放在后面。 　　　
Bad: I thought that he could finish this　job in just two hours impossible. 　　
Good: I thought it impossible that he could finish this job in just two hours.　 
C. 带有宾语从句的复合句的否定形式一般是否定主句。
Bad: I think he doesn’t like the English teacher. 　　
Good: I don’t think he likes the English teacher. 
D.  主句一般过去时态，从句也要用过去时态。
False: He wanted to know why he is crying in the corner. 　　
Right: He wanted to know why he was crying in the corner

宾语从句的否定转移:
主句的谓语动词是think,believe,imagine,suppose,consider,espect,fancy,guess等。
并且主句的主语是第一人称而且为一般现在时，从句的否定词一般要转移到主句上来,其反义疑问句一般与宾语从句一致。
I don’t think he will come to my party.而不能说成I think he won’t come to my party.
我认为他不会来我的舞会.
I don’t believe that man is killed by Jim,is he?
我认为那个人不是Jim所杀的,是不是?
如果宾语从句中有某个含有否定意义的形容词或副词,其反义疑问句要用肯定形式。
We find that he never listens to the teacher carefully,does he?
我们发现他从来不仔细听老师讲课，是不是?

宾语从句中引导词的用法比较
在复合句中作主句的宾语，引导词有：
连词：that (that 常可省略),whether, if
代词：who, whose, what ,which
副词：when ,where, how, why 等。

（一）that引导的宾语从句（在非正式场合that可以省略）
1.可跟that从句做宾语的动词有：
say, think, insist, wish, hope, demand, imagine, wonder, know, suppose, see, believe, agree, admit, deny, expect, explain, order, command, feel, dream, suggest, hear, mean, notice, prefer, request, require, propose, declare, report等。
例句：The boy believes that he will travel through space to other planets.
注意事项：当主句谓语动词是 think, believe, suppose, expect 等词，而宾语从句的意思是否定时，常把否定转移至主句表示。
例句：I don’t think it is right for him to treat you like that.

2.在以下情况中that不能省略
a.当句中的动词后接多于两个由that引导的宾语从句时，第一个that可省，但后面的that不可省。
例句：He said (that) you were too young to understand the matter and that he was asked not to tell you.
b.当主句的谓语动词与that宾语从句之间有插入语时，that一般不可省。
例句：Just then I noticed, for the first time, that our master was wearing his fine green coat and his black silk cap.
c.当that从句是双宾语中的直接宾语时，that不可省。
例句：I can’t tell him that his mother died.
d.注:许多带复合宾语的句子，that引导的宾语从句经常移到句子后部，而用it作形式宾语。
例句：I find it necessary that we should do the homework on time.

（二）由whether,if 引导的宾语从句
1.由whether(if)引导的宾语从句，实际上是一般疑问句演变而来的。意思是“是否”。宾语从句要用陈述句语序。
一般说来，在宾语从句中whether与if可以互换使用，但在特殊情况下if与whether是不能互换的。
例句：I wonder whether(if) they will come to our party.

2.只能用whether，不能用if引导的宾语从句
a.在带to的不定式前
例句：We decided whether to walk there.
b.在介词的后面
例句：I’m thinking of whether we should go to see the film.
c.在动词后面的宾语从句时
例句：We discussed whether we had a sports meeting next week
d.直接与or not连用时
例句：I can’t say whether or not thet can come on time.

3.只能用if不能用whether引导的宾语从句
a.if引导条件状语从句，意为“如果”
例句：The students will go on a picnic if it is sunny.
b.if引导否定概念的宾语从句时
例句：He asked if I didn’t come to school yesterday.
c.引导状语从句even if（即使）和as if（好象）时
例句：He talks as if he has known all about it.

if,whether在宾语从句中的区别
a.if和whether在作“是否”解时,引导宾语从句常放在动词know,ask,care,wonder,find out等之后,介词后一般不用if
b.少数动词,如:leave,put,discuss,doubt后的宾语从句常用whether. 
c. whether后可以加or not,但是if不可以.
d.在不定式前只能用whether.
（如：I can’t decide whether to stay. 我不能决定是否留下。）
e.避免歧异时,我们常用whether而不用if.

（三）连接代词和连接副词引导的宾语从句
这样的宾语从句实际上是由特殊疑问句变化而来的，宾语从句要用陈述句语序。
用于这种结构的动词常常是：see, say, tell, ask, answer, know, decide, show, find out, imagine, suggest, doubt, wonder, discover, understand, inform, advise等。
1.英语中的连接代词有：who,whom,whose,which,what,在句中担任主语、宾语、定语或者表语。
例句：Can you tell me whom you are waiting for?
2.英语中的连接副词有：when,where,why,how，在句中担任状语的成分。
例句：None of us knows where these new parts can be bought.

简化宾语从句常用六法：
方法一：
当主句谓语动词是hope， decide， wish， choose， agree， promise等，
且宾语从句的主语与主句主语一致时，宾语从句可简化为不定式结构。
例如：
Li Ming hopes he will be back very soon.
→Li Ming hopes to be back very soon.
We decided that we would help him.
→We decided to help him.

方法二：当主句谓语动词是know， learn， remember， forget， tell等动词，
且主句主语与从句主语一致时，宾语从句可简化为“疑问词+不定式”结构。例如：
She has forgotten how she can open the window.
→She has forgotten how to open the window.
注：当主句谓语动词是tell， ask， show， teach等动词，
且后带双宾语，从句主语和间接宾语一致时，宾语从句可简化为“疑问词+不定式”结构。例如：
Could you tell me how I can get to the station？
→Could you tell me how to get to the station？

方法三：当主句的谓语动词是order（命令），require（需要）等时，
如果主句和从句的主语不一致，宾语从句可简化为“名词（代词）+不定式”结构。例如：
The headmaster ordered that we should start at once.
→ The headmaster ordered us to start at once.

方法四：某些动词后的宾语从句，可以用介词加动名词（短语）等其他形式简化。例如：
He insisted that he should go with us.
→He insisted on going with us.
The poor boy doesn’t know when and where he was born.
→The poor boy doesn’t know the time and the place of his birth.

方法五：某些动词后面的宾语从句可转化为“宾语+V-ing形式（作宾语补足语）”结构。例如：
Liu Ping found that there was a wallet lying on the ground.
→ Liu Ping found a wallet lying on the ground.

方法六：动词seem后的宾语从句，也可以用不定式（短语）来简化，但句型需要进行适当的变化。例如：
It seemed that the boys were going to win.
→The boys seemed to win.
除上述方法外，还有一些特殊句式的转化。例如：
I found that it was difficult to learn English well.
→I found it difficult to learn English well.
Soon we found that the ground was covered with thick snow.
→Soon we found the ground covered with thick snow.
They found that the box was very heavy.
→They found the box very heavy

“It”用法及其句型和固定搭配，是英语语法的重点、难点，又是近几年考试的热点，因此在复习中应给予足够的重视。
It 句型归纳：
1． It is ＋adj．(＋for sb．／sth．) ＋ to do sth．
用于此句型的形容词有：easy， hard， difficult，possible， important， impossible， necessary， good， bad， exciting， interesting， surprising等。如：
 It is necessary to change your job．
 It was very hard for them to walk such a long way in the snow．
2．It is ＋n．(＋for sb．／sth．) ＋ to do sth．
用于此句型的名词有： pity, shame, pleasure, one’s duty, one’s job, fun, joy, good manners, bad manners等。如：
 It is a pity for you to have missed such a wonderful play．
 It is bad manners for the young to take up the seats for the old．
3．It is ＋adj．＋of sb．＋to do sth．
此句型中的形容词主要描述某人的品德、特征。能用于该句型的形容词有： kind, nice, wise,
silly, polite, impolite, friendly, foolish, clever等。如：
 How silly it was of you to give up such a good chance！
 It is friendly of the family to try to make me feel at home in their house．
4．It is ＋adj．（＋n．）＋doing sth．
此句型中的形容词和名词常见的有：no／little use, no／much good, useless等。如：
 It’s no use crying over spilt milk．
5．It takes sb．＋一段时间＋to do sth． 表示“做某事花费某人多长时间”。如：
It took us half an hour to ride to the town by the sea．
6．It is ＋及物动词的过去分词＋that从句
此句型中常见的及物动词的过去分词有：said, told, known, reported, recorded, thought, believed, considered等。如：
It is reported that the Russian President will visit China next week．
7．It ＋不及物动词＋that从句
此句型中不及物动词常见的有：seem， happen， appear， matter等。如：
 It seems that there will be a heavy snow tomorrow．
 It happened that I met my good friends in the museum yesterday．
8．强调句型：It is＋被强调部分＋that／who从句
在使用强调句型时要注意，指人时可以用who或that，其它情况一律用that。如：
 It was under the bed that my brother hid the ball this morning．
 It is Mr Bell who／that often comes and looks after the old man．
9．It is／has been＋一段时间＋since从句。如：
It is ／has been three years since we saw each other last．
10．It is (high) time that sb． did sth．
该句型表示“某人现在该做某事了”，从句常用过去时（虚拟语气）说明现在应该做的事情。如：
 It’s six o’clock．It is high time that we went home now．

It 常用的固定搭配：
1. make it
（1）在口语当中相当于succeed，表示：成功、做到、说定、赶上、及时到达
例  It's hard to make it to the top in show business.
（2）在口语中相当于fix the date for，表示“约定好时间”
例  —Shall we meet next week？
—OK. We just make it next Saturday.
2. as it is
（1）相当于in fact，in reality表示“事实上，实际情况是……”
例  We had planed to finish the task today，but as it is we probably won't finish it until next week.
（2）相当于方式状语从句，表示“照原样”
例  Leave the table as it is.
3. as it were
相当于as one might say，that is to say，表示“也就是说，可以说，换句话说”
例  He is，as it were，a modern Sherlock Holmes.
4. if it weren't for…/if it hadn't been for…
用来引导虚拟语气，相当于without，or but for，表示“如果不是……，要不是……”
例  If it weren't for Tom，I wouldn't be alive today.
5. that's it
（1）相当于That's all. That's so much. 表示“至此为止，没有别的了”
例  You can have one more sweet，and that's it.
（2）相当于 That's right.表示“对啦”
例  — I guess the key to the problem is thechoice “A”
—That's it.
6. catch it
在口语中，相当于be punished/scolded for doing sth. wrong. 表示“因做错事而挨骂，受责备，受批评，受惩罚”
例  We'll really catch it form our teacher if we're late for class again.
7. have it
（1）相当于say，insist表示“说，主张，表明，硬说”
例  Rumour has it that they are getting divorced.
（2）相当于get to know something，表示“了解，知道，获悉”
例  I had it from John that she was going abroad.
8. have what it takes
在口语中，相当于be well qualified for，表示“具有成功的条件”
例  You can take it from me that your daughter has what it takes to be a star.
9. so it seems / appears.
10. Keep at it！（Don't give up！）
相当于go on，表示“继续做，不放弃”
例  My teacher asked me to keep at it.
11. Go it！（Go on！）拼命干，莽撞
12. Now you have done it！（You have done sth. wrong.）
13. Now you'll catch it！（You'll be punished.）
14. As it happened，…
在口语中，相当于it's a pity that…，表示“真不凑巧，真遗憾”
例  As it happened，they were out.
15. As it turned out，…
在口语中，相当于it was found to be in the end，表示“最后被证明是”
例  As it turned out，his statement was false.
16. Such as it is（they are）
在口语中，相当于although it may not be worth much，表示“虽然没有多大价值”
例  You can borrow my exam notebook，such as it is.
17. Take it/things easy.
相当于Don't worry or don't hurry. 用来劝告别人，表示“不要慌，别担心，存住气”
例  Take it easy！ He will do it well.
18. Take it from me.
在口语中，相当于believe me what I say.表示“请相信我的话，我敢担保”
例  You can take it from me that he will make it this time.
19. For what it is worth…
在口语中，相当于although I'm not sure it's of value，表示“不管其价值如何”
例  Here is the article I promise you，for what it's worth.
20. Worth it
在口语中，相当于useful，表示“有好处，值得做”
例  Don't hesitate about it！ It's worth it.
21. Believe it or not.表示“信不信由你”
例  Believe it or not，Tom is getting married to Mary next Sunday.
22. Take it or leave it. v. 要么接受要么放弃
例  That is my last offer. You can take it or leave it.
23. It all depends/that all depends
在口语中，相当于it hasn't been decided yet，表示“那得看情况，还没有定下来”
例  —Are you going to the countryside for holiday？
—It/That all depends.
24. It's up to sb.
在口语中，相当于it's decided by sb. 表示“由……决定，由……负责，取决于……”
例  —Shall we go out for dinner？
—It's up to you.

it用法小结：
It用作实词
表达以下概念:
指代前文提到的事物，前文中的this, that；
替代前文中的内容；
指代一位性别不明的小孩或未知的人；
指代未指明但谈话双方都知道的那件事；
指代时间、天气、气候、距离等自然现象。

一、it 作人称代词的用法
1. 指事物
作为人称代词，it 可以除人以外的一切事物或动物。如：
I dropped my watch and it broke. 我把手表掉在地上摔坏了。
It’s hard work, but I enjoy it. 工作很辛苦，可是我乐意干。
“Where is the dog?” “It’s in the bedroom. ” “狗在哪?”“在卧室里”。
2. 指人
it 指人主要用于指不性别不明的婴儿或用于确认某人的身份。如：
Is it a boy or a girl? 是男孩还是女孩?
There is a knock on the door. It must be the postman. 有人在敲门，一定是邮递员。
【说明】在答语中，常用来指本人，如说 It’s me。
3. 代替某些代词
代词 it 还可用于代替指示代词this, that 以及复合不定代词 something, anything, nothing等。如：
“What’s this?” “It’s a new machine. ” “这是什么?”“是一种新机器”。
Nothing is wrong, is it? 没出什么问题，是吗?

二、it 作非人称代词的用法
1. 基本用法
it 作非人称代词的用法，主要用于指时间、距离、价值、天气、气候及温度等自然现象。如：
It’s too late to go there now. 现在去那儿已经太迟了。
It rained all day yesterday. 昨天下了一天的雨。
It can get very hot here. 这里有时会很热。
2. 用于某些句型
It’s time for sth. 该做某事了。
It’s time to do sth. 该做某事的时候了。
It’s time for sb to do sth. 某人该干某事了。
It’s (about / high) time + that-从句. 某人该做某事了。(从句谓语用过去式，有时也用“should+动词原形”)
It’s first (second) time + that-从句. 某人第几次干某事。(从句谓语用现在完成时)
It’s + 时间段 + since-从句. 自从……有一段时间了。
It’s + 时间段 + before-从句. 过多长的时间才……

三、it用作形式主语
1. 基本用法
当不定式、动名词、从句等复杂成分用作句子主语时，为保持句子平衡，通常把真正的主语放在句末，而在句首使用形式主语it。如：
It’s very important to remember this. 记住这一点很重要。
It’s hard work climbing mountains. 爬山是费劲的事。
It’s unknown when he will come. 他什么时候来还不知道。
2. 用作形式主语的的重要句型
(1) It + be + adj. for (of) sb to do sth 某人做某事……
It is hard for him to make up his mind. 他很难下定决心。
It was foolish of her to say such a thing. 她说那样的话，真是太蠢了。
【说明】介词 of 与 for 的区别是：
of 用于指某人的性格、属性、特征等，介词for表示对象，意为“对……来说” 。
(2) It takes sb + 时间段 + to do sth. 某人做某事花了……时间
It takes years to master a new language. 要花多年的时间才能掌握一门新的语言。
【说明】此句型可以有以下多变种变体：It took me an hour to write the letter.
=The letter took me an hour (to write). =I took an hour to write the letter. 我写这封信花了一个小时
(3) It is up to sb to do sth. 该由某人做某事
It’s up to you to to make the choice. 得由你来作选择。
(4) it look (seem, appear, happen, occur) that [as if]… 似乎……
It seemed as though he didn’t recognize me. 他似乎没认出我来。
It happened that I was out when he called. 他打电话时我碰巧不在家。
(5) If it were not for… / If it hadn’t been for… 若不是因为……
If it were not for their help, we couldn’t have got over the difficulties. 要不是他们帮助，这些困难我们不克服不了的。

四、it用作形式宾语
1. 基本用法
当不定式、动名词、从句等复杂成分用作宾语且其后跟有宾语补足语时，通常会在宾语补足语前使用形式宾语，而将真正的宾语移至句末。
其基本结构为“动词+it+宾语补足语+不定式(动名词或从句)”。如：
I find it difficult to do the job well. 我发现做好这件事不容易。
I think it best that you should stay here. 我认为你最好住这儿。
We think it no use complaining. 我们认为抱怨是没有用的。
2. 用作形式宾语的几个特殊结构
(1) 动词+ it + that-从句。如：
I like it that you came. 你来了，我很高兴。
I take it (that) he will come on time. 我认为他会准时来的。
You can put it that it was arranged before. 你可以说这是以前安排的。
Rumor has it that the defence minister will soon resign. 据传闻，国防部长不久就要辞职。
【说明】能用于此结构的动词不多，常见的有 have, take, put, like 等。
(2) 动词 + it + when (if)-从句。如：
I dislike it when you whistle. 我不爱听你吹口哨。
We really appreciate it when she offered to help. 她来帮忙了，我们十分感激。
I’d prefer it if I didn’t have to do so much work. 要是我不必做那么多工作，好就太好了。
【说明】能用于此结构的动词不多，常见的有 enjoy, hate, love, like, dislike, appreciate, prefer 等。
(3) 动词 + prep + it + that-从句。如：
See to it that you’re not late again. 注意千万不要再迟到。
Look to it that this doesn’t happen again. 注意不要再发生这种事。
You may rely on it that he’ll come to meet you. 你放心，他会来接你的。
I can’t answer for it that he will come. 我不能保证他会来。
【说明】能用于此结构的动词不多，常见的有see to, look to, insist on, stick to, depend on, answer for 等。
(4) 动词 + it + 介词短语+ that-从句。如：
I owe it to you that I am still alive. 多亏有你我才仍然活着。
I took it for granted that he would help us. 我认为他会帮助我们的。
【说明】能用于此结构的动词不多，常见的有take it for granted, bring it to sb’s attention, owe it to sb 等。

it在强调句中的使用
It is＋被强调部分＋that(who)＋其他
在使用强调句型时需注意以下几点：
1. 请注意强调句型的特殊疑问句 
2. 在强调原因状语从句时，只能强调由because所引导的从句。
3. 在强调not … until结构时必须把not与until一起放到被强调的位置上。
4. 注意强调句型与定语从句的区别。
5. 不管被强调部分是单数还是复数，其前一律用It is / It was，而不能用They are / There were之类的。
6. 被强调部分是指人时，被强调部分后可用that / who，被强调部分指物时，被强调部分后只能用that。
7. 被强调部分是指时间或地点时，被强调部分后通常用that，一般不用when，where之类的。例：
It is I who am right. 是我对。
It was you that were wrong. 是你错了。
It was in the Japan that he died. 他是死于日本。
It was yesterday that he got married. 他是昨天结婚的。
It was a computer that he bought last week. 他上个星期买的是一台电脑。
Where was it that she lived? 她是住在什么地方?
When was it that he left for Japan? 他是什么时候离开去日本的?
Who is it that teaches you English? 是谁教你们英语?