it is用法.doc

It is ... that/since/before等句型归纳
1.  为了突出或强调句中的某一成分以加强语气, 英语中通常用 “It is + 被强调成分 + that/who”结构，这一结构叫作强调结构。该结构中的 It 是无人崐称主语, 没有词汇意义,仅起到改变句子结构,使某一成分受到强调的作用。如被崐强调的是物，用 that; 如被强调的是人, 用 who, 也可用 that。
强调结构中被强调的成分通常是句中的主语、宾语、地点状语或时间状语。例如下面一句, 我们可分别对其不同成分进行强调：
John wore a white suit at the dance last night.
1.It was John that/who wore a white suit at the dance last night.（强调主语）
2. It was a white suit that John wore at the dance last night. (强调宾语）
3. It was at the dance that John wore a white suit last night. (强调地点状语）
4. It was last night that John wore a white suit at the dance.（强调时间状语）
强调结构亦可用来强调某些状语从句：
It was because he was ill that he didn't come to school yesterday.（强调 because 引导的原因状语从句）
It was only when the war was over in 1949 that he was able to get back home.  
                                                        (强调when 引导的时间状语从句）
It was not until his father came back that he went to bed. (强调 until引导的时间状语从句）
现谈谈强调结构中值得注意的几个问题：
一. 强调结构中的时态问题
如果被强调的成分，原句谓语动词是一般现在时或一般将来时，强调结构用 It is...that/who; 如果原句的谓语动词是过去时态，则用 It was...that/who; 有时还可用 be 的其它形式。例如：
It is the people who/that are really powerful.
It was in the street that I met your brother yesterday.
It must be your mother who you are thinking of.
二. 强调结构中代词的格和谓语人称与数的问题
如果被强调的部分是原句的主语, that/who  后面的谓语在人称和数上均应与原句主语一致, 不与 it 一致。例如：
It is you that/who are to blame.
It is I that am mistaken.
一般说来, 强调主格人称代词就用主格, 强调宾格人称代词就用宾格, 但有时被强调的格与原句中的格不一致。例如：
I met her in the street this morning.
It was her that I met in the street this morning.
    her 在原句中是 met 的宾语,  所以被强调时仍用宾格形式, 但也可用主格she 替换 her。例如：
It was she that I met in the street this morning.
这时, 说话者遵循传统语法, 认为动词 be 后面的代词用主格,而不管这个代词在原句中究竟是主格还是宾格。
强调主格时也有两种情况, 尤其是在非正式的口语中常用宾格代替主格。例如：
They saved the drowning girl.
It was they who saved the drowning girl.
It was them who saved the drowning girl.
三. 强调结构中的一般疑问句和特殊疑问句问题
一般疑问句只需将 "It" 与 "is/was" 交换位置即可。例如：
Was it you that broke the window?
Was it here that you met him?
如强调疑问句, 需将疑问词置于句首：
Who was it that called him "comrade"?
What is it that you are going to do?
When is it that they will leave?
四. 强调结构中的 that/who 在口语中常可省略：
It was you I thought of all the time.
It is here he must come.
It was John I gave the book to.
Was it in Chengdu you first met him?
What is it you want me to do?
五. 注意固定言语中的意思：
It is a wise father that knows his own child.聪明的父亲往往也不了解自己的儿子。
It is a long lane that has no turning. 胡同不管怎样长，总是要拐弯的。（天无绝人之路）
It is a long night that never finds the day. 漫漫长夜，总有拂晓时。
It is a silly fish that is caught twice. 任何鱼都不会愚蠢到上两次钩。
2． It is (high) time that…
该句型中的that可省略，从句谓语通常是动词的过去式，也可用should + 动词原形。相当于It is time for sb. to do sth.例如：
It is time that we went to school.
It is time I ought to leave now.
It’s high time that we should put an end to the controversy.
3． It is + n.+ that…
该句型为主语从句。It为形式主语，真正的主语是that引导的从句。例如：
It is a pity that you didn’t see the film yesterday.
It is a wonder that he refused such a good offer.
It is common knowledge that the traffic situation there is deplorable.
用于该句型的名词常见有：common knowledge, common sense, a good thing, an honor, a mercy, a pity, a pleasure, a shame, a surprise, a wonder等。
4． It is + adj.+ that…
该句型为主语从句。It为形式主语，真正的主语也是由that引导的从句。例如：
It is certain that we shall be late.
It’s strange that he didn’t come yesterday.
Isn’t it strange that the lazy boy (should) pass the exam.
能用于该句型的形容词常见的有：certain, clear, curious, disappointing, dreadful, fit, fortunate, frightening, funny, good, important, lucky, natural, necessary, obvious, peculiar, pleasing, possible, probable, proper, right, sad, surprising,          remarkable, unfortunate, unimportant, unnecessary, unusual, useless, well, wonderful, wrong, true等。that从句可用陈述语气，也可用should + 动词原型的虚拟语气形式。用陈述语气表示客观事实；用虚拟语气表示惊讶、喜悦、遗憾、失望等感情色彩或表示要求、建议、命令、愿望等。
5． It is + p.p. + that…
该句型为主语从句。It为形式主语，真正的主语是that引导的从句。例如：
It was said that Mr. White had been writing a new TV play.
It is reported that the sports meet has been put off.
It has not been decided that when and where we ill hold the meeting.
能用于该句型的过去分词常见的有：admitted, announced, believed, decided, demanded, disclosed expected, found, hoped, reported, requested, said, seen, suggested, thought, told, unknown,等。
6． It is…before…
该句型的is后可接long或一段时间。肯定句译为“过多久…才…”；否定句译为“没多久…就…”。例如：
It was a long time before I got to sleep again.
It will be hours before he arrives here.
It was not long before he left his home town.
It will be five years before we meet again.
It wasn’t long before he told us about this affair.
It was evening before we reached the little town.
7．It is … since…
该句型表达“从……以来已经多久了”的意思。这一结构多用一般过去时，表示从过去某一时刻起到说话这一时刻止的这段时间的总和。时间的起点，无论是那种动词，一律从since从句中的谓语动词表示的动作的完成的那一刻算起。例如：
It is 15 years since the war ended.
It is just a week since we arrived here.
It is ten years since he left his home town.
It must be almost 5 years since we last met.
从句中可用现在完成时。例如：
It is three years since I’ve seen him. = It is three years since I saw him.
since从句如为延续性动词，用一般过去时，表示“动作的结束”。例如：
It’s years since I enjoyed myself so much.
It is four years since she was a nurse.
How long is it since you were in London.
8．It is … when
该句型中when引导的是时间状语从句，其前面是表示时间的词作表语，强调句型中that前面被前调的是状语。例如：
It was ten o’clock in the evening when he came back.
It is twelve o'clock at midnight when they arrived at a lovely village.
It was 2005 when he left his home town.

练习：
1.     ----He was nearly drowned once.
----When was____?
----____ was in 1998 when he was in middle school.
A. that, it                      B. this, This               C. this, It                   D. that, This
2.     The Foreign Minister said “____ our hope that the two sides work towards peace.”
A. This                         B. There is                    C. That is                            D. It is
3.      It is almost five years ____ we saw each other last time.
A. before                      B. since                        C. after                        D. when
4.      ____ in the regulations that you should not tell other people the password of tour E-mail account.
A. What is required        B. What requires           C. It is required             D. It requires
5.      It is pretty well understood ____ controls the flow of carbon dioxide in and out the atmosphere today.
A. that                          B. when                       C. what                        D. how
6.      It is difficult for us to learn a lesson in life ____ we’ve actually had that lesson.
A. until                         B. after                         C. since                        D. when
7.      I have always been honest and straightforward, and it doesn’t matter ____ I’m talking to.
A. who is it                   B. who it is                   C. it is who                   D. it is whom
8.      It is none of your business ____ other people think about you. Believe yourself.
A. how                         B. what                        C. which                      D. when
9.      ----Did Jack come back early last night?
----Yes. It was not yet eight o’clock ____ he arrived home.
A. before                      B. when                       C. that until
10.  Scientists say it may be five or six years ____ it is possible to test this medicine on human patients.
A. since                        B. after                         C. before                      D. when
11.  He was told that it would be at least three more months ____ he could recover and return to work.
A. when                       B. before                      C. since                        D. that
12.  It was evening ____ we reached the little town of Winchester.
A. that                          B. until                         C. since                        D. before
13.  The field research will take Joan and Paul about five months; it will be a long time ____ we meet them again.
A. after                        B. before                      C. since                        D. when
14.  Great changes have taken place in that school. It is no longer ____ it was 20 years ago, ___, it was so poorly equipped.
A. what, when                     B. that, which               C. what, which             D. which, that
15.  That was really a splendid evening. It is years ____ I enjoyed myself so much.
A. when                       B. that                          C. since                        D. since
16.  It was some time ____ we realized the truth.
A. when                       B. until                         C. since                        D. before
17.  ____ has been announced, we shall have our final exam next month.
A. That                        B. As                            C. It                             D. What
18.  I’m afraid I’m not fit for the job, as it is one ____ requires lots of patience.
A. who                         B. that                          C. what                        D. where
19.  It is high time ____ I went back home.
A. on which                  B. which                      C. when                       D. X
20.  ----Was it midnight ____ you arrived home by taxi?
----I’m afraid so.
A. that                          B. at which                   C. the time                    D. when
21.  It was several years ____ I finally realized ____ you enjoyed and built on those abilities.
A. when, that                B. that, when                C. before, that               D. until, why
22.  It is not yet pretty well understand ____ made the rainforest disappear year by year.
A. what                        B. which                      C. that                          D. how
23.  ____ sometimes keeps her awake at night ____ Tom is getting more and more quiet at home.
A. That, which                     B. It, that                      C. Whether, what          D. What, that
24.  ____ worries me the way he keeps changing his mind.
A. This                         B. That                         C. What                       D. It
25.  It was in this park ____ they met for the first time ____ the old couple told us their unforgettable experience.
A. where, that               B. that, that                   C. where, when            D. that, when
26.  Why! I have nothing to confess. ____ you want me to try.
A. What is it that           B. What it is that           C. How is it that            D. How it is that
27.  It was drinking ____ cost the man a lot of money ____ he ought to have spent on his family.
A. that, that                  B. what, what               C. that, what                 D. what, that
28.  It is no wonder ____ he has succeeded.
A. when                       B. what                        C. which                      D. that
29.  ----Where did you meet Joan?
----It was in the hotel ___she stayed.
A. that                          B. where                      C. which                      D. there
30. Is it good to look up every new word ____ I came across it in reading?
A. when                       B. before                      C. that                          D. where

1------5 A D B C C    6-----10 A B B B C
11---15 B C B A D    16----20 D B B D D
21---25 B A B D A    26----30 A A D B A