代词 pron.
1.它
This suitcase looks heavy but actually it is very light.
这个皮箱看上去很重,实际上很轻.
2.他
Her baby's due next month.She hopes it will be a boy.
她怀的孩子下个月出生,她希望是个男孩儿.
3.事实[情况]
It is a very long way from the West Coast to the East of America.
从美国的西岸到东岸的距离是很长的.
It is ten o'clock in the morning.
现在是早上十点钟.
It is raining.
下雨了.
It was on Sunday that an American friend of mine came to see me.
那个星期天,我的一个美国朋友来看我.
Where did she go?—It was to Britain that she went.
她去了什么地方?——她去的地方是英国.
I don't like it that he should be alone with my girlfriend.
我可不喜欢他单独和我的女朋友在一起.
It is not easy if you ask her to stop.
你让她停下来可不容易.
It's very clear what the red-haired man means.
这个红头发男人的意思很明显.
4.（指婴儿,尤指性别不详者）
5.（用以明确身分）
6.（用作形式主语或形式宾语,而真正的主语或宾语在句末）
7.（谈论时间、日期、距离、天气等时用作主语）
8.（谈论情况时用）
9.（指已知或正在发生的事实或情况）
10.（强调句子的某部份）
11.正好是所需的；恰好