介词和介词短语的概念：

介词是一种用来表示词与词、词与句之间的关系的虚词，在句中不能单独作句子成分。介词后面一般有名词、代词或相当于名词的其他词类，短语或从句作它的宾语。介词和它的宾语构成介词词组，在句中作状语，表语，补语或介词宾语。介词可以分为时间介词、地点介词、方式介词和其他介词。

误用介词的三种情况：

1、多用介词：
多用介词可能是受汉语意思的影响将及物动词误用作不及物动词，也可能是受相关结构的影响而用错：
误：We discussed about the plan.
正：We discussed the plan. 我们讨论了计划。
误：Did he mention about the accident?
正：Did he mention the accident? 他提到那次事故了吗?
误：I saw her enter into the bank.
正：I saw her enter the bank. 我看见她进了银行。
误：He married with[to] a nurse.
正：He married a nurse. 他同一位护士结了婚。
误：How can contact with you?
正：How can contact you? 我怎么与你联系?
误：We should serve for the people heart and soul.
正：We should serve the people heart and soul. 我们应该全心全意地为人民服务。
误：Who controls over the factory? (但名词control可接over)
正：Who controls the factory? 谁管理这个工厂?
误：He has a great many of friends here. (比较a great number of)
正：He has a great many friends here. 他在这儿有很多朋友。

2、漏用介词：
漏用介词可能是受汉语意思的影响将不及物动词误用作及物动词，或是受相关结构的影响的影响而用错等：
误：This matter is difficult to deal. (deal with=处理)
正：This matter is difficult to deal with. 这事很难处理。
误：He is not a man to be depended.
正：He is not a man to be depended on. 他不是个可靠的人。
误：He took a cup of tea, and went on the story.
正：He took a cup of tea, and wentonwiththestory.他喝了一口茶，又接着讲故事。
误：My mother still regards me a child. (比较consider…as中的as可省略)
正：My mother still regards me as a child. 我母亲还把我当小孩看。
误：They insisted sending a car over to fetch us.
正：They insisted on sending a car over to fetch us.他们坚持要派车来接我们。
误：What he says is worth listening.
正：What he said is worth listening to.他的话值得一听。

3、错用介词：
错用介词的情况比较复杂，可能是因受汉语意思的而错，也可能是因弄不清搭配关系而错，可能是混淆用法而错，也可能是受相关结构的影响而错，可能是忽略语境而错，也可能是想当然的用错：
误：She called on his office yesterday. (call on+人，call at+地点)
正：She called at his office yesterday. 她昨天去了他办公室拜访。
误：He is engaged with a nurse.
正：He is engaged to a nurse.他与一位护士订了婚。
误：The sun rises from the east.
正：The sun rises in the east.太阳从东方升起。
误：Under his help, I finished it in time.
正：With his help, I finished it in time. 在他的帮助下，我及时做完了。
误：During he was in Japan, he visited many places.
正：During his stay in Japan, he visited many places.他在日本期间,参观过许多地方。
误：We are familiar to his character.
正：We are familiar with his character.我们了解他的性格。
误：Help yourself with the fruit.
正：Help yourself to the fruit.吃点水果吧。

介词的宾语：

 1、名词或代词作介词宾语：
如：Are you interested in history? 你对历史感兴趣吗？
        Don't worry about it. 别为它担心。
注：若是人称代词用作介词宾语，要注意用宾格。
如：No one can sing like her. 没有人能像她那样唱歌。(不能用like she)
2、动名词作介词宾语：
如：He is good at telling stories. 他善于讲故事。 
        In crossing the street he was run over. 他在穿过马路时被汽车撞倒。
3、过去分词作介词宾语：
如：We can't regard the matter as settled. 我们不能认为这事已经解决。
        I take it for granted you have read the book. 我以为你读过这本书。
注：过去分词用作介词宾语通常只见于某些固定结构中，如上面第1句涉及regard…as(认为…是)结构，第2句涉及take sth for granted(认为某事属实)。在其他情况下，介词后通常不直接跟过去分词作宾语，若语义上需要接过去分词(表被动)，可换用“being+过去分词”：
如：He went out without being seen by the others.他出去了，没有被其他人看见。
4、从句作介词宾语：
如：He was not satisfied with what she said. 他对她说的不满意。
        I'm worried about where he is. 我担心他上哪儿去了。
注：介词后通常不接that从句，遇此情况需考虑用其他结构：
误：He paid no attention to that she was poor.
正：He paid no attention to the fact that she was poor. 他根本不注意她很穷这一事实。
但有个别介词(如except)可接that从句。
比较：I know nothing about him except that he lives next door./I know nothing about him except for the fact that he lives next door. 我只知道他住在隔壁,其它的就不知道了。
5、不定式作介词宾语：
如：I had no choice but to wait. 除了等，我没有别的选择。 
       He wanted nothing but to stay there. 他只想留在那儿。
       They did nothing but complain. 他们老是一个劲地抱怨。 
       He never did anything but watch TV. 除了看电视，他从不干任何事。
注：(1)介词后接不定式的情形通常只见于but, except等极个别个词。该不定式有时带to，有时不带to，其区别是：若其前出现了动词do，其后的不定式通常不带to；
若其前没有出现动词do，则其后的不定式通常带to。 
(2)介词后虽然通常不直接跟不定式作宾语，但却可接“连接代词(副词)+不定式”结构：
如：He gave me some advice on how to do it. 对于如何做这事他给我提了些建议。
6、形容词作介词宾语：
如：Her pronunciation is far from perfect. 她的语音远不是完美的。
        In short, we must be prepared. 总而言之，我们要有准备。
        Things have gone from bad to worse. 事情越来越糟。
注：(1)有些形容词用作介词宾语可视为其前省略了动名词being：
如：He regarded the situationas(being) serious. 他认为形势严重。
        His work is far from(being) satisfactory. 他的工作丝毫不令人满意。 
(2)有些“介词+形容词”的结构已构成固定搭配：in full全部地，全面地，无省略地； in private私下地，秘密地； in particular特别地；in general一般地，通常地，概括地； in brief 简言之；in short总之，简言之； in vain徒然地，徒劳无益地；for fee免费地，无偿地； for certain肯定地，确切地；for sure肯定地，确切地； for short为了简短，简称；atl arge自由自在地，逍遥法外； by far…得多
7、副词作介词宾语：
如：I can't stay for long. 我不能久呆。 
        It's too hot in here. 这里面太热了。
        I looked every where except there. 除了那儿，我到处都看过了。
8、数词作介词宾语：
如：The city has a population of four million. 这座城市有四百万人口。
        He was among the first to arrive. 他是第一批到的。
9、介词短语作介词宾语：
如：Choose a book from among these. 从这些书中选一本吧。
        I saw her from across the street. 我从街的对面望见了她。
注：通常可后接介词短语作宾语的介词是from, till, until, since, except, instead of等。
比较：I took it from the bed. 我从床那儿(或床上)拿的。
            I took it from under the bed. 我从床下拿的。 
10、复合结构用作介词宾语：
如：She had no objection to Mary marrying him. 她不反对玛丽与他结婚。
        She came in with a book in her hand. 她手里拿着一本书走了进来。
        All the afternoon he worked with the door locked. 整个下午他都锁着门在房里工作。

介词短语的句法功能：
1、表语：
如：He was with a friend. 他和一个朋友在一起。
        Health is above wealth. 健康胜过财富。
        This knife is for cutting bread. 这把小刀是用于切面包的。
注：有些介词(如because of)引出的短语通常只用作状语，不用作表语：
误：His absence is because of the rain.
正：His absence is due to the rain. 他因雨未来。
但是，若主语是代词(不是名词)，becauseof引出的短语可用作表语：
如：It is because of hard work. 那是因为辛苦工作的原因。
2、状语：
如：Don't touch it with your hands. 别用手去摸它。
        Did you do this by design or by accident? 你这样做是有意的还是无意的？
3、定语：
如：This is his reply to your letter. 这是他给你的回信。
        This is the best way of doing it. 这是做此事最好的方法。
        My love for you is deeper than the sea. 我对你的爱比海深。
4、宾语补足语：
如：I found everythingin good condition. 我发现一切正常。
       Her illness kept her in bed for a week. 她因生病在床上躺了一星期。
注：用作宾语补足语的介词短语在相应的被动语态中则为主语补足语：
如：He was regarded as a hero. 他被看成是英雄。
5、宾语：
如：A man stepped out from behind the wall. 一个人从墙后走出来。
        He cannot spare anytime except on Sunday. 除星期日外，他抽不出时间。
6、主语：
如：Between6 and 7 suits me. 六点到七点对我比较适合。
        After the exams is the time to relax. 考试后是轻松一下的时间。
注：介词短语通常不用作主语，尽管有时也像上面这样用作主语，但通常可视为是在一定的上下文中有所省略：
如：—When are we going to have the next meeting? 我们下次什么时候见面？
        —On Tuesday may be convenient. 星期二可能比较方便。
此句中onTuesday虽用作主语，但可视为是其前省略了meeting一词：
即：Meeting during the vacation may be convenient.

动词短语的概念：

动词常和某些其他词类用在一起，构成固定词组，形成所谓短语动词(phrasalverb)。和动词一样，短语动词也可分为及物和不及物两种。短语动词可以作为一个整体看待，同一般动词一样使用。

 动词短语的搭配类型：

1）动词+介词：
这类短语动词用作及物动词，后面须跟宾语。
如：The small boy insisted on going with his parents. 那男孩坚持要跟父母一起去。
        Do you often listen to broadcasts in English? 你常听英语广播吗?
        Look at the children. Aren't they lovely? 看着这些孩子们。他们多么可爱呀!
        We stand for self-reliance. 我们是主张自力更生的。
这一类的短语动词还有很多，如depend on(upon)(依靠)，wait on(服侍)，look for(寻找)，deal with(对待)，look after(照料)，wait for(等待)等。
2）动词+副词：
这类短语动词有的用作及物动词，有的用作不及物动词。
如：I always get up as soon as the bell rings. 我总是一打铃就起床。(不及物)
        Look out, there's a car coming! 当心，来汽车了!(不及物)
        Have you handed in your exercises already? 你已经交练习了吗?(及物)
        Please don't forget to put on your coat, it's cold outside. 请不要忘记穿外衣，外面很冷。(及物)
这一类的短语动词还有很多，及物如put out(扑灭)，eat up(吃光)，put down(放下)；不及物如set off(出发)，come up(走近)，go on(继续)。
注："动词+副词"这类短语动词和上面第一类"动词+介词"的不同之处在于："动词+介词"用作及物动词，后面须跟宾语。"动词+副词"则有的及物，有的不及物；用作及物动词而宾语为人称代词或自身代词时，副词往往放在宾语之后。
如：Please wake me up at five tomorrow. 请在明天早上五点唤醒我。
        If you have done your exercises, please hand them in. 如果你们练习做完了请交来。
        She doesn't normally behave like that, she's putting it on. 她通常并不如此表现，她是装出来的。
注：这类短语动词有不少可兼作及物和不及物动词用。
如：He took off his hat when he entered the office. 他进办公室后脱下帽子。(及物)
        The plane took off at seven sharp. 飞机在七点整起飞。(不及物)
        Charlie rang up Neil to ask about the time of the meeting. 查理打电话给尼尔问开会的时间。(及物)
        If you can't come, please ring up and let us know. 你如来不了，请来电话告诉我们一声。(不及物)
3）动词+副词+介词：
"动词+副词"之后有的可以再加一个介词，形成另一种短语动词。这类短语动词用作及物动词。
如：Do not give up hope. We must go on with the experiment 不要失望。我们必须继续试验。(go on with继续)
        He came up to me. 他走到我跟前。(come up to走近)
这类短语动词还有：look down upon(看不起)，do away with(去掉)，put up with(忍受)等。
4）动词+名词+介词：
这类短语动词也是及物的。
如：He shook hands with all the guests at the banquet. 他在宴会上和宾客一一握手。
        Young pioneers often come to the Children's Palace to take part in after school activities.少先队员经常到少年宫来参加课外活动。
        Pay attention to the temperature of the stored rice. 注意仓库里的稻谷的温度。
        Her job is taking care of the babies. 她的工作是照顾婴儿。
这一类短语动词还有：put an end to(结束)，take notice of(注意)，catch hold of(抓住)，lose sight of(看不见)，make use of(利用)等。

动词短语知识体系：

 

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.