It is to let the fresh air in that I often keep the windows wide open.…第二节：应该注意的问题用It's…that/who结构对句子进行强调时应该注意一下几个问题：1.这种结构只有一般现在时和一般过去时两种时态。
其他的时态很少用这种句式进行强调。
It has been four years _____ I gave up smoking.A.that.B. since.分析：遇到这种高考题，我们就毫不考虑的选B. since.2. 在强调主语时，that 后的谓语动词要与被强调者保持人称和数的一致。
如：It is I who am a teacher.3. 即使被强调的主语是复数，主句中的谓语动词也用单数。
换句话说：强调句中不可能出现am, are, were。
如：It is they who often help me with my lessons.4.强调句和it作形式主语的区别。
强调句中的It's, that/who在句中只是一种语法手段，没有任何意义，如果去掉不会对句子的意思产生影响，或不会影响句子的完整性。
但是，it作形式主语的结构如果去掉句子就不完整。
因为that引导主语从句时不能省略，而且is/was在句子中充当谓语（系动词）。
It is a good idea that we eat out.分析：如果去掉it is 和that, We eat out said. 很明显时个不完整的句子。
5.强调时间状语的强调句和时间状语从句的区别。
时间状语从句中主句和从句都是完整的句子，it指代时间，如果把其中的it, is/was和when去掉，句子将不完整；而强调句则完整。
It was 12:00 we went home.A. thatB. when.分析：如果去掉it was和横线，We went home 12:00。
很明显这是个错误的句子，缺少介词at. 真确的句子因该是：We went home at 12：00.6.强调句和as引导的定语从句的区别。
这两种句型的区别比较简单，在定语从句一章有详细讲解，此处不再赘述。
总之，区别强调句和其他句式最有效的方法是：去掉it, is/was, that/who或横线后看句子是否完整。
如果完整肯定是强调句，不然为其他句式。
7.强调句的反义问句。
强调句的反义问句比较简单，只要将它看成it is/was…的句子就可以了。
It is…that…, isn't it?It is not…that…, is it?It was…that…, wasn't it?It was not …that…, was it?第三节：高考常见题型1.强调句的一般形式。
虽然这是最简单的形式，但由于其在英语表达中占有很重要的位置，因此在高考中常常出现。
It was in New Zealand ___ Elizabeth first met Mr. Smith.(2008 全国II 20)A. thatB. howC. whichD. when分析：去掉it was 和横线：Elizabeth first met Mr. Smith in New Zealand.句子完整。
所以A. that。
2.强调句的一般疑问句。
强调句虽然简单，但是换成一般疑问句后学生往往无从下手。
)上海卷Was __________ that I saw last night at the concert? (1997．A. it youB. not youC. youD. that yourself分析：方法还是一样：去掉句中的it, was, that再看句子是否完整。
如果完整，就是强调句。
不完整在从其他的角度分析。
I saw you last nightat the center. 非常完整。
所以A. it you 。
3.强调句的特殊问句。
可以说这是近年高考最受青睐的题型。
它的特点是使用广泛、灵活多变、但有一定的难度，对于高考这类选拔型考试特别适合。
它可以以单独的形式出现，也可以与其他的从句形式相配合。
下面我们就来看看这种结构。
（2）单独的特殊疑问句。
格式：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？如：When was it that you were born?Why! I have nothing to confess. __________you want me to say? (2004上海卷)A. What is it thatB. What it is thatC. How is it thatD. How it is that分析：这是典型的强调句特殊疑问句。
根据句意A. What is it that 。
（2）充当名词性从句的强调句特殊问句。
由于这种句型在句子中做了名词性从句，那么话句话说就是陈述语序的特殊问句。
格式：被强调部分（通常是疑问代词或疑问副词）+ it is/ was + + that/who + 其它部分。
When asked to explain ______ made his lessons so exciting, the teacherkept silent.A. what it is thatB. that what it isC. what is it thatD. that what is it。
A. what it is that分析：这道题是强调句用作宾语从句。
根据题意4.It is/was not A but B that…这是带有选择性的强调句。
当然也可以出现其他的连词，如ratherthan….有时也可以出现几种变形形式：a.It's A that…not B.b.It's not A but B that…c.It's A rather than B that …d.It's A that…rather than B.It is not who is right but what is right ______ is of importance.[2007 重庆卷]A. whichB. itC. thatD. this分析：典型的选择式强调句。
所以C. that。
5.not…until的强调。
可以说这是高考中出现频率最高的强调句类型。
这种强调句比较特殊，在强调not …until 结构中由until 短语（或从句）表示的时间状语时，要用固定的强调句型：It is(was) not until ...that... 注意此时原句的not…until要变成not until ，that 从句中的谓语动词要用肯定式。
如：a. My father didn't come home until 12 o'clock last night.b. It was not until 12 o'clock last night that my father came home.c. I didn't realize she was a famous film star until she took off her darkglasses.d. It was not until she took off her dark glasses that I realized she was afamous film star.It _____ we had stayed together for a couple of weeks ____ I found wehad a lot in common. [2007 浙江卷]A. was until; whenB. was until; thatC. wasn't until; whenD. wasn't until; thatD. wasn't until; that。
分析：标准句型，所以的其他用法it第四节：1. it可用作人称代词、指示代词、先行词及引导词等。
（1）人称代词it，是第三人称单数中性，代表前文已提到过的一件事物。
如：a. That vase is valuable. It's more than 200 years old.b. I love swimming. It keeps me fit.当说话者不清楚或无必要知道说话对象的性别时，也可用it来表示。
c. It's a lovely baby. Is it a boy or a girl?it可用来指代团体。
如：d. The committee has met and it has rejected the proposal.it用以代替指示代词this, that.如：e. --- What's this? --- It's a pen.(2) 指示代词it，常用以指人。
如：a. Go and see who it is.b. --- Who is making such a noise?--- It must be the children.(3) 虚义it无指代性，常用作没有具体意义的主语，出现于表示天气、气候、温度、时间、地点、距离等意义的句子中。
如：a. It is half past three now.b. It is six miles to the nearest hospital from here.c. It was very cold; it snowed and grew dark.(4)it也常用来表示一般的笼统的情况。
如：a. It's awful—I've got so much work I don't know where to start. 糟透了——我有这么多工作要做我不知从何开始。
b. How is it going with you? 你近况如何？c. Take it easy. 不要紧张。
d. I like it here. 我喜欢这个地方。
e. It looks as if the college is very small.f. It seems as though our plan will be perfect.g. It's my turn. 该轮到我了。
(5) it也常用于某些习惯用语中作宾语，各该习惯用语有具体意义，但it并无具体意义。