1. 要点提示

it可以用作人称代词，它还可以指时间、天气、距离、上下文等，另外，it还可以作先行词，作形式主语和形式宾语。

2. 用法指南

(1)作为人称代词，it可以用来指东西、动物、婴儿和未确定身份的人。

Where's my book? Have you seen it?

我的书在哪里？你看见了没有？

The dog is in the garden, isn't it?

狗在花园里，是吧？

The baby cried because it is hungry.

婴儿哭了，因为他/她饿了。

(Someone is ringing.)Who's it? It's me.

(有人在按门铃。)谁呀？是我。

(2)it 可以指上下文内容

The Olympic Game will be held in Beijing in 2008. It makes the Chinese proud.

2008年将在北京举行奥运会。这使得中国人非常自豪。

(3)it表示时间、天气、距离等。

What time is it now? It's half past nine.

现在几点了？九点半

It is cold.天气冷。

It's about ten kilometers from the park to the museum.

公园到博物馆大约是十公里。

(4)it用作形式主语或形式宾语

It's very important for us to learn English well.(实际主语是to learn English well)

对我们来说，学好英语很重要。

I found it hard to fly a kite. (实际主语是to fly a kite)

我发现放风筝很难。