题目内容：

Hi, I’m your tooth. I’ve been asked to represent the rest of your teeth. We need your help. We like to be clean when you show us off with your big, wide smiles.

First, let me tell you a little about us. You weren’t born with the baby teeth, they developed when you were about six or seven months old. You went from milk to real food in no time thanks to your twenty primary teeth. Eventually, they loosened and fell out, one at a time, probably about the time you were six or seven years old.

Then we came into your life. We are your permanent teeth, all twenty-eight of us. Some people may even have thirty-two depending on those wisdom teeth in the back. Sometimes they are able to help, and sometimes they cause trouble. Many times wisdom teeth are sideways and have to be pulled. Some people don’t even have them at all!

On a more personal note, I am an incisor, and you have seven more just like me, here in the front of your mouth. We do the biting on those chocolate chip cookies you like so much. Next to us are the canines, four sharp teeth, two on either side. Their job is to tear food; pizza is a good one for them. Behind them are eight premolars and eight to twelve molars, depending on those wisdom teeth. The molars do the majority of the work chewing the food that you eat. They do a great job on those carrots you like so much!

Did you know we not only help you bite and chew but also help you talk? That’s right. Try to say “tooth” without letting your tongue touch the back of your teeth. It sounds pretty funny, doesn’t it?

1.How many teeth does a four-year-old boy usually have according to the passage?

A. 20. B. 24. C. 28.   D. 32.

2.Why are the wisdom teeth pulled sometimes?

A. Because they are useless.

B. Because they are in the back.

C. Because they are ugly.

D. Because they grow in wrong directions.

3.The word “I” in the passage refers to a _____.

A. wisdom tooth B. baby tooth

C. molar        D. permanent tooth