三大结构
三大结构是指强调结构，反义疑问结构和主谓一致结构。
一．强调结构
1．强调句型
It is/was +被强调对象（主语，宾语和状语）+ that/who/whom+….
I saw her in the street last week.
强调主语: It was I that/who saw her in the street last week.
强调宾语：It was her that/whom I saw in the street last week.
强调状语：It was in the street/last week that I saw her.
    注意： I am a teacher.
强调主语: It is I that/who am a teacher.
2．倒装结构
倒装结构是强调结构的另一种表现形式。根据主语和谓语在句中的位置，倒装可分为全部倒装（Full Inversion ）和部分倒装（Partial Inversion）。全部倒装是将整个谓语置于主语之前；而部分倒装则是只将系动词be, 助动词 do, does, did, has, have，had,will, would, should 或情态动词移至主语之前，有时谓语改用动词原形。
除疑问句中采用倒装外，主要有下列几种特殊情况，句子需要倒装：
1) 全部倒装
（1）祝愿句。例如：
Long_____ the People’s Republic of China.
A) live  B) does …live  C) do…live  D) lives
答案是A。句意：中华人民共和国万岁！
  ______succeed/Wish you success!
  A) Will you B) May you  C) Can you  D) You may
  答案是B。句意：祝你成功。
  （2）当句首为here, there, up, down, away, now 等副词，谓语动词为be, go, come, stand, lie 等不及物动词时，且主语是名词时，主谓要完全倒装，但主语若是代词，则主谓不用倒装。例如：
Now ____.
A) does your turn come  B) do your turn come  C) comes your turn  D) come your turn
答案是C.
注意区别： Here comes the bus. /Here you are.
（3) 某些地点状语或介词短语放置句首，且主语是名词时，也会引起全部倒装。例如：
From the valley _____ a terrible sound.
A) come  B) came  C) did …come D) does … come
答案是B。
（4）主语部分较长或主语结构比较复杂而需要后置时，且主语是名词时，全句需要倒装。例如：
Leaning against the window in deep concentration _____ my friend Lily, who looked as though she had spent a sleepless night.
A) was  B) were  C) is  D) are
答案是A。
（5）为了强调句子中特殊成分的需要，且主语是名词时，有些句子使用倒装。例如：
Facing the lake ____ a little inn.
editor的名词和动词形式A) was  B) is  C) were  D) are
答案是B。
2) 部分倒装
（1）当带有否定意义的副词或短语位于句首时，要采用半倒装形式，以加强语气或强调。常见词及词组有at no time(从不), on no account（决不）,by no means（决不）,in no case（决不）,in no way（决不）, under (in) no circumstances（决不）, no more， no sooner, not only, scarcely/(几乎不), hardly(几乎不), seldom, in vain（徒劳地）, little, never
注意：固定搭配：no sooner…than (刚。。。就。。。)
                hardly/scarcely…when (刚。。。就。。。
Never ____ found him in such a good mood.
A) I have  B) I had  C) have I  D) had I
答案是C。
No longer these days _____ necessary for women to wear veils in most areas.
A) it is  B) is it  C) they are  D) are they
答案是B。注意：在这句话中，主语是it, 而不是these days,因此不选D。
)
Hardly(Scarcely)/No sooner had I left home when/than it began to rain.
2）句首的状语若由“only +状语/副词/介词词组/状语分句”构成，也可引起部分倒装。例如：
Only yesterday ______ that his watch was missing.
A) he found out  B) he finds out  C) did he find out  D) does he find out
答案是C。
（3）当关联连词“so +形容词/副词＋that”和“such +(名词) ＋that”结构中的so, such 用于句首加强语气时，通常采用部分倒装。例如：
So small ____ that I could hardly see it.
A) the mark was  B) was the mark  C) the mark is  D) is the mark
答案是B。看到后面句中有could,因此我们选用和后面时态相匹配的一般过去时，不选D。
（4）在一些虚拟条件句中，如果句中省掉连词if，且系动词或助动词为were, had 或should 时，则要将were, had 或should 移至主语之前。例如：
__ Were __ you in my position, you would do the same.
A) Are  B) Were  C) Was  D) Is
答案是B。
(5）在由as 引导的让步状语从句中，名词、形容词、副词倒置于as 之前，形成倒装语序。应注意的是：如果as 前面的表语是名词，即使是单数可数名词，也不要带冠词.例如：
1.____ Child  _ as she is, she knows a great deal.
A) A child  B) Child  C) Children  D) Childs
答案是B。
2.Busy as he was, he still came here.
3.__ Hard ___ as he tried，he was unable to make much progress.
A) Hard  B) Hardly  C) Very hard D) Very hardly
答案是A.
Try as you may, you won’t succeed.
(6) 代词so, neither/nor 等副词置于句首，表示上述情况与前句相同时，需要倒装。例如：
If you can/can’t do the work by yourself, so/neither(nor) can I ____.
A) I can  B)  can I C) could I  D) I could
答案是B。
二．反意疑问结构
反意疑问结构有陈述部分加疑问部分构成, 如果陈述部分为肯定形式或含义肯定, 则疑问部分使用否定形式;如果陈述部分为否定形式或含义否定, 则疑问部分使用肯定形式. 疑问部分由 “助动词+代词” 构成. 反意疑问结构的常见考点有:
1) 当陈述句中主语为everything, anything, something, nothing 等表示事物的不定代词时，疑问部分的主语为it. 例如:
Something is wrong with the machine, isn’t it? 机器出故障了, 是吗?
Nothing can make her change her mind, can it? 什么都不能使她改变注意, 对吗?
2) 当陈述句中主语为anybody, anyone, everybody, everyone, somebody, someone, nobody, no one, these, those 等表示人的不定代词时, 反意疑问句主语用they. 例如:
Everybody agreed, didn’t they?
每个人都同意,是吗?
No one was injured in the car accident, were they?
没有人在交通事故中受伤,是吗?
3) 祈使句的反意疑问句一般只用肯定式. 例如:
Lend me a hand, will you? 帮我一把, 好吗?
  由let 引导的祈使句则用shall we. 例如:
  Let’s go swimming together, shall we? 咱们一起去游泳吧?
  但用let us 表示请求对方, 反意疑问句用will you. 例如:
Let us get in, will you ? 让我们进去吧?
4) 当句子是一个含有宾语从句的复合句时, 反意疑问句一般与主句的谓语动词和主语保持一致, 但若主句的主语是第一人称, 而谓语动词又是think, believe, expect, suppose 等词时, 疑问部分则应该与宾语从句保持一致. 例如:
He never said that she would come, did he?
他从没有说过她回来,不是吗?
I don’t believe he can finish the task, can he?
我认为她不能完成这项工作, 不是吗?