从属连词的概念：

连词用于引导从句以形成句子的一部分或修饰句子的构成要素的叫作从属连词。

英语从属连词用法分类详解：

1、引导时间状语从句的从属连词：
 （1）表示“当…时候”或“每当”的时间连词。主要的when, while, as, whenever：
如：He jumped up when the phone rang. 电话铃响时他吓了一跳。 
        We listened while the teacher read. 老师朗读时我们听着。
        The phone rang just as I was leaving. 我正要离开，电话铃就响了起来。
（2）表示“在…之前(或之后)”的时间连词。主要的有before, after：
如：Turn the lights off before you leave. 离开前请关灯。
        He started the job soon after he left the university. 他大学毕业后就开始做这份工作。
（3）表示“自从”或“直到”的时间连词。主要的有since, until, till：
如：He has lived here since he got married. 他结婚后就一直住在这儿。
        Most men worked until[till] they're 65. 大多数男人工作到65岁。
（4）表示“一…就”的时间连词。主要的有as soon as, the moment, the minute, the second, the instant, immediately, directly, instantly, once, no sooner…than, hardly…when等：
如：Tell him the news as soon as you see him. 你一见到他就把这消息告诉他。
        I recognized her the moment(that) I saw her. 我一看到她就认出她来了。
        I want to see him the minute(that) he arrives. 他一到来我就要见他。
        I went home directly I had finished work. 我一干完活就回家了。
       Once he arrives, we can start. 他一来我们就可以开始。
（5）表示“上次”、“下次”、“每次”等的时间连词。主要的有every time(每次)，each time(每次)，(the) next time(下次)，any time(随时)，(the) last time(上次)，the first time(第一次)：
如：Last time I saw him, he looked ill. 上次我见到他的时候，他好像有病。
        Next time you're in London come and visit us. 你下次来伦敦过来探望我们。
        Do look me up next time you're in London. 你下次到伦敦来，一定来找我。
        Every time I call on him, he is out. 我每次去访问他，他都不在。
       You can call me any time you want to. 你随时都可以给我打电话。
【注】every time,each time,any time前不用冠词，(the)next time, (the)last time中的冠词可以省略，而the first time中的冠词通常不能省略。
2、引导条件状语从句的从属连词：
这类连词主要有if, unless, as[so] long as, incase等：
如：If anyone calls tell them I'm not at home. 要是有人打电话来，就说我不在家。
        You will fail unless you work hard. 你若不努力就会失败。
        As[So] long as you need me, I'll stay. 只要你需要我，我就留下。
        In case I forget, please remind me about it. 万一我忘记，请提醒我一下。
【注】在条件状语从句中，通常要用一般现在时表示将来意义，而不能直接使用将来时态。不过，有时表示条件的if之后可能用will，但那不是将来时态,而是表示意愿或委婉的请求(will为情态动词)：
如：If you will wait a moment, I'll fetch the money. 请等一下，我就去拿钱。
3、引导目的状语从句的从属连词：
主要有in order that, so that, in case, for fear等：
如：We used the computer in order that we might save time. 我们使用计算机是为了节约时间。
        Speak clearly so that they may understand you. 说清楚，以便让他们能明白你的意思。
        Be quiet in case you should wake the baby. 安静些，免得把婴儿吵醒。
        He is working hard for fear he should fail. 他努力工作以免会失败。
4、引导结果状语从句的从属连词：
主要的有so that, so…that, such…that等：
如：We're all here now, so that the meeting can begin at last. 我们现在都到齐了，终于能开会了。
        It's so difficult a question that none of us can answer it. 那是一个很难的问题，我们没有一个人能回答。
        He shut the window with such force that the glass broke. 他关窗户用力很大，结果玻璃震破了。
【注】so that中的that在口语中通常可以省略。
5、引导原因状语从句的从属连词：
主要的有because, as, since, seeing(that), now(that), considering(that)等：
如：He couldn't got to school because he had a cold. 他因患感冒而未能去上学。
        Since everybody is here, let's begin our discussion. 大家都到了，我们就开始吧。
        Seeing that it is 8o'clock, we'll wait no longer. 由于时间已到8点，我们将不再等了。
        Now that you are here, you'd better stay. 你既然来了，最好还是留下吧。
6、引导让步状语从句的从属连词：
主要有although, though, eventhough, even if, while, however, whatever, whoever, whenever, wherever等：
如：Although[Though] he is poor, he is well contented. 他虽穷却能知足常乐。
        Though[Even though] it's hard work, I enjoy it. 尽管是苦活，但我乐意干。
        Even if you don't like wine, try a glass of this. 即使你不喜欢喝酒，也尝尝这杯吧。
7、引导方式状语从句的从属连词：
主要有as, like, as if, as though, the way等：
如：Do it as[like] he does. 像他那样做。
        He behaved as if nothing had happened. 他装作若无其事的样子。
        They treat me as though I were a stranger. 他们待我如陌生人。
        Nobody else loves you the way(=as) I do.没有人像我这样爱你。
8、引导地点状语从句的从属连词：
主要有where, wherever, everywhere等：
如：There were lots of parks where I lived. 我住的地方有许多公园。
        Sit wherever you like. 你想坐在那儿就坐在那儿。
        Everywhere they went, they were warmly welcomed. 他们每到一个地方都受到热烈欢迎。
9、引导比较状语从句的从属连词：
主要有than和as…as：
如：It's easier than I thought. 这比我想像的要容易。
        They are as often wrong as they are right. 他们错对各半。
10、引导名词性从句的从属连词：
主要有that, if, whether：
如：It is clear enough what he meant. 他是什么意思很清楚。 
       Your greatest fault is that you are careless. 你最大的缺点是粗心大意。
       Whether it will do us harm remains to be seen.是否对我们有害还要看一看。
       She didn't say if he was still alive. 她没说他是否还活着。

从属连词知识体系：

用作从属连词的六类名词结构：

英语中有些名词结构可用作从属连词，用以引导状语从句，且主要是时间状语从句。这类结构归纳起来有以下六类：
一、the+瞬间名词：
其中的瞬间名词主要包括moment, minute, instant, second等，其意为“一……就……”，相当于as soon as。
如：The minute he saw her he fell in love. 他对她一见倾心。  
Telephone me the moment(that) you get the results. 你一有结果，马上给我打电话。 
I was so tired that I fell asleep the instant I closed my eyes. 我很累，一合上眼就睡着了。
Sheputdownthereceiverthesecondsherecognizedmyvoice.她一听出是我的声音，马上就放下电话听筒。
注：其中的瞬间名词后可接that，也可省略。另外，有的个别副词（如directly/immediately等）也可表示类似意思。
如： Immediately the meal was over,he switchedon the radio.饭一吃完他就把收音机打开。

二、the+季节名词：
其中的季节名词包括spring,summer,autumn,winter，其意为“在……的那年春天、夏天、秋天、冬天。
如：His wife left him thes pring he went abroad.在他出国的那年春天，他的妻子离开了他。
He sold his house and went to the souththe summer he lost hisjob.在他失业的那年夏天，他卖掉房子去了南方。
He was sentto prison the winter his third daughter was born.在他第三个女儿出生的那年冬天，他被关进了监狱。
She got married the autumn she graduated from college.她大学毕业的那年秋天就结婚了。

三、the+时间名词：
其中的时间名词主要包括hour,day,night,week,month,season,year等，其意为“在……的时候、那天、那个晚上、那周、那个月、那个季节、那年”。
如： The hour he wa sin her office,he felt very sad.当他在她办公室的时候，他感到很伤心。
The day here turned home,his father was already dead.他回家的那一天，他的父亲已经死了。
The night I wenttoseeher,shehadleftforBeijingtoattendanimportantmeeting.就我去看她的那个晚上，她到北京去开一个重要的会议了。
Mr Smith didn't go to work the week his wife was ill.史密斯先生在他妻子生病的那个星期没去上班。
They ear helivedinthecountry,he learned alot.他在乡下呆的那一年，他学到了不少东西。

四、the+序数词+time
其中的序数词包括first,second,third,fourth等，其意为“当第几次……的时候”。
如： My girlfriend beat me at pokert he first time weplayed.我头一次和女朋友打扑克，她就把我赢了。
These cond time I saw her,she looked like an old woman.我第二次见到她时，她看上去像一个老太婆。
The third time I went there,I found all of them had left and the offices were all empty.我第三次去那儿时，我发现他们都离开了，所有的办公室都是空的。
注：
1.next,last也具有类似序数词的性质，因此也具有以上用法。
如： Nexttimeyoucomein,pleaseclosethedoor.下次你进来，请关门。
Thelasttimewetalkedhesaidheneededanothertwodays.上次我们谈话时他说他还需要两天。
2.thefirsttime,thesecondtime,thethirdtime等用作连词引导时间状语从句时，其前通常要有定冠词，而(the)nexttime,(the)lasttime引导状语从句时，其中的冠词可以省略，如下面这道上海高考题，其答案是C，不是A：
I though ther nice and honest______Imether.
A.first time  B.fo rthe first time C.the first timeD.by the first time

五、不定代词+time
其中的不定代词主要包括each,every,any等。
如：Every time I ringher,the phone is engaged.我每次给她打电话，电话都占线。
Every time I see him he either wants to tell me his trouble or borrow some money.每次我见到他，他不是向我诉苦，就是要向我借钱。
He felt nervous each times he spoke to him.每次她和他讲话，他都感到紧张。
AnytimeyoucometoLondondolookmeup.你无论什么时候到伦敦来，一定要来看我。
注意：everytime,eachtime,anytime用作连词引导状语从句时其前习惯上不用冠词，它与the first time,these cond time,the third time等引导时间状语从句时其前必须要用定冠词不同。

六、其他名词结构
以上归纳的名词结构均用于引导时间状语从句，有些其他结构还可引导其他性质的状语从句，如the way可用于引导方式状语从句，表示“像……一样”。如：
The didn’t do it the way we do now.那时他们不像我们现在这样行事。
Joyce looked at me the way alotof girls did.乔伊丝像许多姑娘那样瞧着我。
注：这样用的theway与as用法相似。
如：Hold itin both hands,the way(=as)Mummy does.用两只手捧住，像妈妈那样。

动词不定式的概念：

动词不定式指由to加上动词原形（而且只能是动词原形）所构成的一种非限定性动词，但在有些情况下to可以省略。动词不定式在语法功能上可作主语、宾语、宾语补足语、
表语、定语和状语。

不定式的特殊句型对比：

1、不定式的特殊句型too…to…：
1）too…to　太…以至于…。
例如：He is too excited to speak. 他太激动了，说不出话来。　 
        —Can I help you? 需要我帮忙吗?
        —Well, I'm afraid the box is too heavy for you to carryi t, but thank you all the same. 不用了。这箱子太重，恐怕你搬不动。谢谢。
2）如在too前有否定词，则整个句子用否定词表达肯定，too后那个词表达一种委婉含义，意为“不太”。
例如：It's never too late to mend. 改过不嫌晚。（谚语）　
3）当too前面有only, all, but时，意思是：非常…等于very。
例如：I'm only too pleased to be able to help you. 能帮助你我非常高兴。　
            He was but too eager to get home. 他非常想回家。
2、不定式的特殊句型so as to：
1）表示目的：它的否定式是so as not to do。
例如：Tom kept quiet about the accident so as not to lose his job. 汤姆对事故保持沉默是为了不丢掉他的工作。　　　
            Go in quietly so as not to wake the baby. 轻点进去，别惊醒了婴儿。
2）表示结果：
例如：Would you be so kind as to tell me the time? 劳驾，现在几点了。
3、不定式的特殊句型：Why not：
“Whynot+动词原形”表达向某人提出建议，翻译为：为什么不……?   干吗不……?
例如：Why not take a holiday?

不定式的用法：

1、不定式作补语：
1）有些有动词+宾语+不定式的结构。
例如：advise allow cause challenge command compel drive驱使
enable encourage forbid force impel induce instruct invite like/love order permit make let have want get warn persuade request send tell train urge 等。
例如：Father will not allow us to play on the street. 父亲不让我们在街上玩耍。　　　　　　
            The officer ordered his men to fire. 长官命令士兵开火。
注意：有些动词如make，have，get，want等可用不定式作做宾补，也可用分词作宾补。现在分词表达主动，也表达正在进行，过去分词表达被动。
2）有些有动词+宾语+不定式的结构，不定式的动词往往是be，不定式一般可以省去。
例如：consider find believe think declare（声称） appoint guess fancy（设想） guess judge imagine know 等。
例如：We believe him to be guilty. 我们相信他是有罪的。 
            We know him to be a fool. 我们知道他是个笨蛋。（tobe不能省去）
典型例题：Charles Babbage is generally considered___the first computer.
                    A. to invent　
                    B. inventing　
                    C. to have invented　
                    D. having invented　
答案：C. 一般没有consider+宾语+be以外不定式的结构，也没有consider+宾语+doing的结构，排除A、B、D。consider用动词be以外的不定式作宾补时，一般要求用不定式的完成式，故选C。 3）有些动词可以跟there+to be的结构。例如：believe expect intend like love mean prefer want wish understand 等。
例如：We didn't expect there to be so many people there. 我们没料到会有那么多人在那里。
            You wouldn't want there to be another war. 你不至于想让另外一场战争发生吧。
2、不定式作主语：
不定式作主语，往往用it作形式主语，真正的主语不定式放至句子的后面。　
例如：It's so nice to hear your voice. 听到你的声音真高兴。
            It's necessary for you to lock the car when you do not use it. 不用车的时候，锁车是有必要的。　
            It's very kind of you to help us. 他帮助我们，他真好。　
            It seemed selfish of him not to give them anything. 他不给他们任何东西，这显得太自私了。
3、不定式作表语：
不定式可放在be动词后面，形成表语。
例如：My work is to clean the room every day. 我的工作是每天清扫房间。　　
            His dream is to be a doctor. 他的梦想是成为一名医生。
4、不定式作定语：
不定式做定语通常要放在被修饰的词后，往往表示未发生的动作。
例如：I have a lot of work to do.我有许多事要做。　　　
            There was nothing to bring home that morning. 那天早上（他回家时）两手空空。
5、不定式作状语：
1）目的状语：常用结构为to do,only to do（仅仅为了）, in order to do,so as to do,so（such）...asto…（如此…以便…）。
例如：He ran so fast as to catch the first bus. 他飞快地跑以便赶上第一班车。　　
            I come here only to say good-bye to you. 我来仅仅是向你告别。
2）作结果状语，可以表示没有预料到的或事与愿违的结果，不定式要放在句子后面。
例如：I awoke to find my truck gone. 我醒来发现箱子不见了。　　
            He searched the room only to find nothing. 他搜索了房间，没发现什么。
3）表原因：
例如：I'm glad to see you.  见到你很高兴。
            She wept to see the sight. 她一看到这情形就哭了。
4）表示理由和条件：
例如：He must be a fool to say so.
            You will do well to speak more carefully.
            You will do well to speak more carefully.

不定式知识体系：

不定式用法拓展：

1、用作介词的to：
to可以用作介词，也可用作不定式的标示。下面的to都用作介词：admit to  object to  beaccus to  med to  beused to  stick to  turn to开始 look forward to  be devoted to  pay attention to  contribute to apologize to devote oneself to

2、省去to的动词不定式：
1）情态动词（除ought外）后。
2）使役动词let,have,make后，感官动词see, watch, lookat, notice, observe, hear, listento, smell, feel, find等后。
注意：被动语态中不能省去to。
例如：I saw him dance. 我看见他跳舞。=He was seen to dance. 　
           The boss made them work the whole night. 老板让他们整夜干活。 =They were made to work the whole night.
3）would rather，had better句型后：
4）Why…/why not…句型后：
5）help后可带to，也可不带to, help sb（to）do sth：
6）but和except后：
but前是实义动词do时，后面出现的不定式不带to。
比较：He wants to do nothing but go out. 他只想出去玩。　　
            He wants to believe anything but to take the medicine. 除了吃这药，他什么都信。
7）由and, or和than连接的两个不定式，第二个to可以省去：
8）通常在discover, imagine, suppose, think等词后作宾补时，可以省去to be。
例如：He is supposed（to be）nice. 他应该是个好人。

3、动词不定式的否定式在不定式标志to前加上not。
例如：Tell him not to shut the window。让他别关窗。　
            She pretended not to see me when I passed by. 我走过的时候，她假装没看见。
4、It's for sb. 和It's of sb. 这样的句子中，由于表语形容词性质的不同，导致了不定式逻辑主语标志用for或of的区别。
1）for sb. 句型中的形容词一般为表示事物的特征特点，表示客观形式的形容词，如easy, hard, difficult, interesting, impossible等：
例如：It's very hard for him to study two languages. 对他来说学两门外语是很难的。
2）of sb句型中的形容词一般为表示性格，品德，心智能力，表示主观感情或态度的形容词，如good, kind, nice, clever, foolish, right。
例如：It's very nice of you to help me. 你来帮助我，你真是太好了。用for还是用of的另一种辨别方法：用介词for或of后面的逻辑主语作句子的主语，用介词前边的形容词作表语，造个句子。如果通顺用of，不通则用for。
例如：You are nice.（通顺，所以应用of）。　　
            He is hard.（非所表达的意思，不通，因此用for。）

强调句的概念：

强调句 (The Emphatic Pattern) 是一种修辞，是人们为了表达自己的意愿或情感而使用的一种形式。通过各种方式对句子中的某个部分进行强调，从而起到修辞的作用。英语常用的强调结构有：It is (was)+被强调部分(主语、宾语或状语)+that/who...；what…be…句型；

强调句的使用:

一、强调句句型：
1、用It is／was...that／who...句型表示强调。
（1）陈述句的强调句型：It is/was+被强调部分（通常是主语、宾语或状语）+that/who（当强调主语且主语指人）+其它部分。
e.g. It was yesterday that he met Li Ping.
（2）一般疑问句的强调句型：同上，只是把is/was提到it前面。
e.g. Was it yesterday that he met Li Ping?
（3）特殊疑问句的强调句型：被强调部分（通常是疑问代词或疑问副词）+is/was+it+that/who+其它部分？
e.g. When and where was it that you were born?
注：被强调的部分（通常是句子的主语、状语、宾语或宾语补足语）放在is／was的后面，如被强调的是人，则后面可用who，whom等代替。
如：原句：He met an old friend in the park yesterday.  
        强调主语：It was he who/that met an old friend in the park yesterday.
        强调宾语：It was an old friend that/who he met in the park yesterday. 
        强调地点状语：It was in the park that he met an old friend yesterday. 
        强调时间状语：It was yesterday that he met an old friend in the park.
2、用助动词do, does或did来强调谓语动词。
如：Do come early. 
        He did send you a letter last week.
        We're pleased that she does intend to come.
3、用主语从句+be+被强调部分，主语从句常用what引导。
如：What John wants is a ball.
        What Mary does every day is(to) give piano lessons.  

二、not...until...句型的强调句：
1、句型为：It is/was not until+被强调部分+that+其它部分：
e.g. 普通句：He didn't go to bed until/till his wife came back. 
       强调句：It was not until his wife came back that he went to bed.
2、注意：此句型只用until，不用till。但如果不是强调句型，till, until可通用；
因为句型中It is/was not...已经是否定句了，that后面的从句要用肯定句，切勿再用否定句了。

三、谓语动词的强调：
1、It is/was...that...结构不能强调谓语，如果需要强调谓语时，用助动词do/does或did。
e.g. Do sit down.务必请坐。
      He did write to you last week. 上周他确实给你写了信。
      Do be careful when you cross the street. 过马路时，务必（千万）要小心啊！
2、注意：此种强调只用do/does和did，没有别的形式；过去时用did，后面的谓语动词用原形。 

使用强调句型有以下几点请注意：

①强调句的谓语is或was永远用单数。
如：It was yesterday that I met your father in the street.
②不管被强调部分是哪种状语，只能用that连接，不得使用where、when等连词。
如：It was in the street that I met your father yesterday.
③被强调部分为人时，可用who(主格或宾格)和whom(宾格)代替that，用that也行。
如：It was your father that/whom/who I met in the street yesterday.
        It was I that/who met your father in the street yesterday.
④强调句中也要注意主谓一致、人称一致和否定转移的问题。
如：It is they who are our friends.
        It was not until ten o'clock that we got home last night.
⑤注意不要混淆强调句和其他从句。It is/was...that...为强调句标志，去掉后仍可组成一个完整的句子，只是没被强调，而其他从句一般不具备这一特征。
比较：1）It was ten o'clock when we got home last night. 我们昨晚到家时已十点了。
            2）It was at ten o'clock that we got home last night. 我们昨晚是在十点到家的。
第一句不是强调句，when不可改为that，因为去掉it was和that后，只能组成“We got home ten o'clock last night.”这样一个不完整的句子；第二句是强调句，that不可改为when。

强调句型用法拓展：

1、句首词用“It”，不能用“This”，“That”等。
2、be动词的形式是is或was，不能用复数形式are或were。若原句的谓语动词用了现在时或将来时，则用is；
若原句的谓语动词用了过去时或过去完成时，则用was。
如：It___the Chinese women that___a great role in the socialist construction.
A. is; plays
B. are; play
C .is; play
D. are; plays
答案：C 
3、被强调的部分如果是代词，强调主语用主格，强调宾语用宾格。
如：It is him that/who/whom I met in the street yesterday.
        It is I who/that am wrong.
4、连接词一般用that，当强调部分是人时，既可用that也可用who。特别注意当强调部分是时间状语或地点状语时，不能用when或where。
如：It was on Oct1st, 1949 that People's Republic of China was founded.
        It was at the gate____he told me the news.　　
        A. that
        B. what
        C. which
        D. when
答案：A
5、主谓一致问题被强调的主语要和that后面的谓语动词在数上保持一致。
如：It is Mary who often _____(help) me with my English. （helps）
        It is I that ____(be) against you. （am）
6、not...until结构的强调。
强调“not...until”引导的时间状语时，要用“it is/was not until...that...”结构，that后面的句子要用肯定式，且须用陈述句语序。 
如：We did not get off the bus until it stopped. ?
        It was not until it stopped that we got off the bus. (注意：强调该结构时not until不能分开)

it的概念：

it可用作人称代词、指示代词、先行词及引导词等。

it 的用法：

1、it可指天气、温度、时间、距离等 。
如：It is cold today, isn't it?
2、用作人称代词，代替前文提到过的事物。
如：The dog is not  acold-blooded animals.  It doesn't need to hibernate.
3、为避免重复，it可用来代替前面说过的短语或句子。
如：I tried to persuade my father to give up smoking, but found it impossible. (it=to persuade my father to give up smoking)
4、代替指示代词this，that。
如：—What's this?
        —It's an album.
        —Whose new bike is that?
        —It's Mary's.
注：it与one，that的区别：
        it=the（this, that）+名词，特指并且代替前面所提到的某特定事物。
如：He's bought a new car, so he drives it everywhere to show ito ff.
        one=a+名词，one指前面提到的同类事物中的不同的另一个。
如：He needs a computer, but he can't afford one.
        that=the+名词，that指代的名词与前面的名词属于同一类，但不属同一个。
如：The population of China is larger than that of Japan.  that指代population，但其后有一个of短语作定语，以区别于the population of China。
注：it与that的异同：
        it指同一事物，that指同类但并不是同一事物。
如：I like the climate of Kunming more than that of Beijing.
       The climate of Kunming is mild, and I like it.
5、It/This/That+be+the first(second, third...) time+that-clause 这个句型表示截止到说话时为止的某人的一种经历，关键是注意time前有序数词，主句是一般现在时is时，从句要用现在完成时；如果主句用一般过去时was时，则从句须相应地用过去完成时。
如：This is the first time(that) these Europeans have visited the Great Wall.
        It was the fifth time(that) I had paid a friendly visit to America.
6、在一些相对固定的词组中，没有特殊含义，经常不翻译。
如：He's never really made it as an actor. 作为演员，他从未获得过真正的成功。
        It is my turn. 轮到我了。

强调句中的it：

可以用来改变句子结构，使句子的某一成分得到强调：
1）强调句的基本句型it's/was+被强调成分+that/who+其他成分
原句：I told Jim the news in our office yesterday.
强调主语：It was I that/who told Jim the news in our office yesterday.
强调宾语：It was Jim that I told the news in our office yesterday.
            或：It was the news that I told Jim in our office yesterday.
强调地点状语：It was in our office that I told Jim the news yesterday.
强调时间状语：It was yesterday that I told Jim the news in our office.
2）强调句的一般疑问句型Is/Was+it+所强调部分+that/who...?
如：Was it you that told Jim the news in your office yesterday?
3）强调句的特殊疑问句型疑问词+is/was+it+that/who...?
如：Who was it that told Jim the news in your office yesterday?
【注】强调句与主语从句虽然在形式上很相似，即都含有it is(was)...that。但，区别在于：强调句去掉it is(was)…that之后，句子结构仍然完整，而主语从句却不能这样。
如：(It is)our hope(that) the two sides will work towards peace.
解析：去掉It is…that之后，句子是不成立的。由此得出该句不是强调句，而是一个简单的主语从句，it是形式主语，从句是真正的主语。

“it”的用法：

1、it 作形式主语：
it 在句中可作形式主语，而真正作主语的主语从句需要放在句子的末尾。主语从句后置常用以下几种结构：
1）It is/was+adj.+subject-clause可用于此句型的形容词有：
clear, certain, funny, good, impossible, likely, natural, obvious, possible, probable, strange, surprising, true, unusual, wonderful等。
如：It is obvious that going for sports will do a lot of good to your health.
2）It+be+adj./n.(forsb./ofsb.)+todosth. 该句型中的形容词通常表示事物的特点或特征的，如：
difficult, hard, easy, impossible, necessary, important等，此时用for；或表示人的性格特征或特点的，如:
nice, good, bad, kind, silly, foolish, wise, clever, careless, rude, brave, cruel, careful, grateful等，这时要用of 。
3）It is/was+名词词组+subject-clause可用于该结构的名词词组有：
a pity/duty, a good thing, no surprise, good news, an honor, a fact, a mystery, a shame, manners等。
 如：It's a pity that I didn't attend the party.
4）It is/was+V-ed+subject-clause可用于该结构的动词的过去分词有：
said, reported, thought, supposed, believed, hoped, expected, known, decided, announced, arranged等。
如：It is said that something had been done to end the pollution.
注：本句还可改写为：Something is said to have been done to end the pollution.
5）It+vi.+subject-clause可用于该结构的动词有：appear, seem, happen, occur等。
 如：It appeared to scientists that the stars had moved.
6）It doesn't matter(makes no difference,etc.) +连接代词或连接副词引起的从句作宾语。
如：It doesn't matter whether he'll join the army or not.
        It makes no difference where we have the conference.
7）一些固定句型：
It takes sb. some time to do sth.
如：It will take you two days to get there on foot. 
It costs sb. some money to do sth.
如：It costs 1,000 dollars to fly to America.
It is/was no use(useless) doing（做什么是没有用处的）
如：It's no use arguing with him.
It is/was no good doing（做什么是没有好处的）
8）以下句型结构中需要用虚拟语气
① It is/was important(necessary, strange) that...;
     It is/was ordered(required, suggested, proposed) that...;
     It is/was a pity(a shame) that...表示遗憾等感情的句子中，主语从句要用“should+动词原形”，should可以省略。
如：It's necessary that he(should) be operated on at once.
② It is (high)time that...结构中用should+动词原形（should不能省略）或动词过去式。
如：It is high time that you should make(made) full use of your time to go over your lessons.

2、it作形式宾语：
1）动词consider（feel, find, think等）+it+形容词（名词）+不定式（动词-ing形式，从句）。
 如：She thinks it no use telling me.
2）主语+appreciate（enjoy，like，love，hate）+it+if（when）...结构
如：We would appreciate it if you could come to help us.
3）dependon, relyon, see to（负责/设法做到）, takeforgranted（习以为常）等短语后跟that从句时，要以it作形式宾语。
如：We're depending on it that he will finish the job by Friday.

“it ”引起的几个易混淆的时间句型：

1）It be+时间+since-clause 这个句型表示从since从句谓语动作发生以后到现在或过去所经过的一段时间，意为“自从…以来已多久了”，主句多用一般现在时，从句用一般过去时，如果表示过去的情况，主句一般用过去时，从句用过去完成时，或主句用过去完成时，从句用一般过去时。
注：since引导时间状语从句时，从句若使用终止性动词，则表示该时间是主句时间段的终点（时间从现在算起）；若从句使用延续性动词，则表示该动作状态的结束（时间从过去算起）。
如：It's five years since they got married. 他们结婚已经5年了。 
        It's five years since they were married. 他们离婚已经5年了。
        It's ten years since his father was a worker. 他父亲不当工人已经10年了。
        I haven't seen him since we were boys together. 我们长大以后再没有见过面。 
2）It be+时间+before-clause 这个句型中的时间一般为表示一段时间的词语（如：long years, months, weeks, days, hours, minutes），主句中的谓语动词用肯定式，意为“过多长时间才…”。主句的谓语动词是否定式时，意为“没过多长时间就…”。主句的时态可用过去时was或将来时willbe；用was时，before从句的动词用一般过去时；用willbe时，before从句常用一般现在时。 如：It was not long before she learned those poems by heart. 她没过多久就背会了那些诗。
        It was long before the police arrived. 过了很久警察才来。
        It will be hours before he makes a decision. 要过好几个小时他才会作出决定。
        It will not be hours before we meet again. 要不了几个小时我们还会再见面的
3）It be+时间+when-clause 这个句型中，it指时间，而且表示时间的词语前没有介词（时间一般是具体时间）。主句和从句中的谓语动词在时态上是一致的，主句是willbe，when从句用一般现在时代替将来时。
如：It was already 8 o'clock when we got home.
        It will be late afternoon when they get there. 
4）It be+时间+that-clause 这个句型是个强调句型。
如：It was at 5o'clock that he practiced playing the violin in the morning. (原句是：He practiced playing the violin at 5o'clock in the morning.)
比较：It was 5o'clock when he started in the morning.（5o'clock前没有介词，这个是定语从句）
5）It be+time+that-clause 这个句型属虚拟语气结构，不管主句中用的是is或was，that从句都须用动词的过去式或should+动词原形（但不及物动词通常用过去式），在time之前有时可以加上high 或about 以加强语气。
如：It is high time(that) he wrote a letter to his girl friend.
        It is time(that) we made people's life a little easier.= It is time that we should make people's life a little easier.