语法是英语学习的基础，英语冲刺复习，有哪些重点语法需要大家关注呢?
It分为两种情况，一种是指代性it,另一种则为非指代性it。在此为大家介绍it的几种用法。
指代性it一般是指人称代词it， it作人称代词时可指代事物、动物、婴儿、未知的人或一件事。
例句1：It’s a theory to which many economists subscribe, but in practice it often leaves railroads in the position of determining which companies will flourish and which will fail. 这句话中第二个it就是指代前面的theory。这是一个许多经济学家赞同的理论，但是在实际中，它往往会使得铁路处于一个决定哪些公司会兴旺，哪些公司会衰败的地位中。
例句2： Until these issues are resolved, a technology of behavior will continue to be rejected, and with it possibly the only way to solve our problems. 在这句话中，it指代a technology of behavior will continue to be rejected 这一情况。除非这些问题得到解决，研究行为的技术手段就会继续受到排斥，解决问题的唯一方法也可能随之受到排斥。
第二种情况是非指代性it。非指代性it是相对于作人称代词的it而言的。他们往往没有具体意义上的主语，它用于表示气候、温度、时间、地点、距离等。非指代性it常作seem, appear, look, happen, occur, follow等动词的主语，构成特定的句型。
例句：From an analysis of the hot-spot population it appears that the African plate is stationary and that it has not moved during the past 30 million years.这句中it没有实际意义，为非指代性用法，that引导表语从句。从热点人口分析中可以看出，非洲板块是静止不动的，而且在过去的三百万年中也从未移动过。
当然，在考研考试中，it的重难点更加具体和明确。
it 做先行词。it做形式主语或者形式宾语。It作形式主语时，往往放在句首，将真正的主语(动词不定式、动名词、从句)放在之后。其中it可作形式主语指代不定式，这时常见的谓语有：take, pay, make, cost, require, feel, annoy, need等。另外，it形式主语指代It形式主语指代从句，而且主要形式为It is+a.+than; It is+n.+that; It is+done+that; It+vi+that;
例如：It is difficult to the point of impossibility for the average reader under the age of forty to imagine a time when high-quality arts criticism could be found in most big-city newspaper.
It做形式宾语是放在谓语动词与宾语补足语之间，指代不定式、动名词、从句等。后接it作形式宾语的谓语动词有：feel, consider, find, believe, make, take, imagine, suppose, think, deem, regard, count等。
引导强调句的it。同学们所熟悉的强调句型中，它的基本形式就是“it+be的某种形式+that/who从句”。当被强调部分是人时须用who, 其他情况用that。例句：Curbs on business-method claims would be a dramatic about-face, because it was the Federal Circuit itself that introduced such patents with its 1998 decision in the so-called State Street Bank case, approving a patent on a way of pooling mutual-fund assets. 在because从句中就运用了it was ….that的强调句型，强调部分为the Federal Circuit itself. 对商业方法专利申请的限制将会是一个巨大的改变，因为这些专利正是联邦巡回法院自己在1998年审理一个被称作“美国道富银行”的案件时提出的，判决中巡回法院批准了一项共同基金资产集资方法的专利。
it作句子的真正主语
1.it 指前面已经提到过的人或事物，有时指心目中的或成为问题的人或事物，作真正主语。
例如：
What’s this? -It is a sheep? 这是什么??这是一只绵羊。
Who is it? -It’s me (I). 谁??是我。
It’s the wind shaking the window. 是风刮得窗户响。
2.it指时间、季节。一般用在无人称动词的主语。
例如：
What time is it? -It’s nine. 几点了??九点了。
It’s time for the meeting. Let’s go. 开会的时间到了，我们走吧。
What day is today? -It’s Saturday. 今天星期几??今天星期六。
What’s the date today? -It is October 1st.
今天是几号? ?今天是十月一日。
What season is it? -It is summer. 现在是什么季节??是夏季。
3.it 指气候。一般作无人称动词的主语。
例如：
Is it cold in this room? -No, it isn’t. 屋里冷吗??不冷。
What’s the weather like today? -It is fine.
今天天气怎么样??是晴天。
It often rains in summer and it often snows in winter in this city.
这个城市夏天经常下雨，冬天经常下雪。
4.it指距离、情况等。一般用作无人称动词的主语。
例如：
It is five kilometers from my home to the school.
从我家到学校有五公里。
It is very near from this factory to that one.
从这个工厂到那个工厂非常近。
It is a long way to the sea. 离海很远。
Is it well with you? 你身体好吗?
it作形式主语
动词不定式、动名词短语起、从句在句子中起主语作用，而这一部分用词较多时，可以用it作为形式主语，放在句首代表其后所说的事实上的、真正的主语，而把真正的主语放在后面。
1.It +谓语+动词不定式。It 作形式主语，动词不定式作真正的主语。
例如：
It is difficult to climb a mountain. 爬山是很艰难的。
It’s a good habit to do morning exercises. 作早操是个好习惯。
It’s important to do proper memory work in the study of a foreign language. 在学习外语时适当地做一些有助于记忆的练习是很重要的。
It is right to do so. 这样做是对的。
2.It+谓语+动名词短语。It 作形式主语，动名词短语作真正的主语。
例如：
It is dangerous playing with fire. 玩火是危险的。
It is no use learning without thinking. 学而不思则罔。
It’s useless arguing with a silly boy. 和笨孩子争论是没有用的。
3.It +谓语+名词性从句。It 作形式主语，以that 引导的名词性从句是真正的主语。
例如：
It is a pity that you didn’t see such a good film.
你没看这么好的电影，真可惜。
It is certain that we shall succeed. 我们一定会成功。
It is strange that nobody knows where he lives.
真奇怪，谁也不知道他住在哪里。
(It is strange that…后面可用虚拟语气。
如：It is strange that he should have made such a mistake.
他居然犯了这样一个错误，真奇怪。
It is strange that nobody should know where he lives.
居然没有人知道他住在哪里，真奇怪。)
It is said that the plane will take off at ten tomorrow morning.
据说飞机明天上午十点起飞。
it 用于强调结构
在表示强调的结构中，it 可用作先行代词，这种结构的句型如下：It +is/was +被强调的部分+that +其他部分。如果强调的部分是人，可用who, whom 代替that.
例如：
Professor Wang teaches us English every Monday afternoon.
王教授每星期一下午教我们英语。
强调主语：It is Professor Wang who teaches us English every Monday afternoon.
强调间接宾语：It is us whom Prof. Wang teaches English every Monday afternoon.
强调直接宾语：It is English that Prof. Wang teaches us every Monday afternoon.
强调状语：It is every Monday afternoon that Prof. Wang teaches us English.
It was here that I first met him. 这就是我初次与他见面的地方。
(强调状语)
It is the people who are realy powerful.
翻译练习
1)该上课了，快。
It is time for class. Hurry up.
2)从这儿到你们学校远吗??不远，大约一公里。
Is it far from here to your school? ?No, it isn’t. It’s about a kilometer.
3)从我家到颐和园去很近。
It is very near from my home to the Summer Palace.