英语语法：it用法
一、指代物
it可替代动植物与无生命的东西，，它与one的区别在于one= a/an + none; it = the + n。
1. ---Where is my pencil case? ---Isn’t it in your backpack?
2. ---I have a motorbike. It (= the motorbike) was bought three years ago.
3. As this chair is broken, I must have it (= the chair) repaired.
4. My father bought a pen and gave it (= the pen) to me.
5. You can not eat your cake and have it. 世事难两全。
试比较：
6. I have no dictionary, so I want to buy one. (one = a dictionary)
7. I have a dictionary, it is over there. (it = the dictionary)
二、指代人
it可指代一个未亲眼看到的、不明身份性别的、面目不详的人，免费学英语网站，英语，或婴儿、儿童，照片中的人物等。
8. --- Who is there waving to you? ---It’s my friend Tom.
9. ---Who is crying in the room? ---It’s my brother Jack.
10. ---Who is knocking at the door? ---It must be Kate, my classmate.
11. ---Who is the girl in the photo on the wall? ---It’s my sister.
12. ---Who is it? ---It’s me. (有人敲门)
13. ---Someone is ringing the doorbell. Go and see who it is. (敲门)
14. ---Oh, by the way, there is a telephone call for you. ---Who was it? (打电话)
15. ---Who is making so much noise? ---It must be the children.
16. There is a person knocking at the door. Who can it be?
17. Just at that time, in came a girl. It was Mark’s sister.
18. There is a young lady at the door. It is his daughter.
19. What a beautiful baby! Is it a boy?
20. A baby is lying in the cradle. It was born two months ago.
21. The baby cry because it is hungry.
22. The baby has got its first tooth.
注意：若身份已确定则要用人称代词。
23. There is a lady at the door. She wants to see you.
注意：向别人介绍某人时用this。
24. This is my friend, Jim.
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