语法复习十六：代 词
It 的用法
１．作人称代词
John likes playing Pingpong．/ He always does it in the afternoon．(指代上下文提到的事物)；/ It's time we went home. / How far is it from here to your home ? / It is getting warmer and warmer．/ It's very quiet at the moment．(可指时间、天气、环境等)
２．引导词
Ａ．作形式主语，代替由不定式、动名词或从句表示的真正主语。
It's important for us to learn a second language．/ It's no use talking to him．/ It's known to all that the earth goes round the sun．
B．作形式宾语，代替由不定式、动名词或从句表示的真正宾语。
We feel it our duty to help others．/ He made it clear that he would leave the city．
C．强调结构：It is (was) +被强调部分＋that (或who)…
注意: 在强调结构中，如被强调部分为时间状语或地点状语，其后的连接词也绝不能为when 或where，而应用that 。在复习中，一定要注意句式的不同。
It was in Shanghai that I bought the guitar．(that引起强调句)
It was Shanghai where I bought the guitar．(where引起定从)
It was twelve o'clock when we arrived there．(when引起时间状语从句）
It was at twelve o'clock that we arrived there．（that 引起强调句）
3. it，one，that 的区别：作为代词，这三个词的对比使用是高考的热点之一。
NMET2000，23．
---Why don't we take a little break? ---Didn't we just have __________?
A．it B．that C．one D．this
NMET2001，25．
The Parkers bought a new house but _________will need a lot of work before they can move in．
A．they B．it C．one D．which
one 用以指代同类事物中的任一，that 特指性强，指代可数与不可数词，而it指代上文提过的同一事物。
不定代词
不定代词种类较多，用法各异，在使用中一定要注意区别。
1、both，either ，neither 都表两者范围，在句中作主语、宾语、定语 ，both可用作同位语。 both 意为"两者都"，either 表"两者中任一个"，neither表"两者都不"。
2、any，none ，all 表三者或三者以上范围，any 表任何一个、一些(不可数或复数概念，用于否定句、疑问句或条件从句中)；none 表三者或三者以上中的哪一个都不；表示不可数物中的一点儿也没有；all 整个的；所有的(三者或三者以上)；所有的(不可数)。
e.g.This book is a good seller，so you can buy it at any shop in Beijing．/ None of us are/is perfect．/ All of the village was flooded．
3、no one，nobody，none，nothing：no one，nobody表没有人，nothing 指没有什么事物，none 兼指人和物。none 着眼于数量概念。"特指的人或物一个也没有，一点儿也没有"。
----How many people are there in the hall ? ----None．
----who wants to go with him ? ----No one(Nobody)．
