题目内容：

There are many ways of putting out a fire. You may have seen people put out burning cigarettes by stepping on them. Stepping on cigarettes shuts off the air and puts out the fire.

Many fires are put out with water. Water cools the materials that are burning. It helps make the fire die out. Some of the water is changed into steam when it strikes the hot fire. The steam keeps air from the fire and helps put it out.

Some fires can not be put out with water. Suppose a tank full of gasoline(汽油)is on fire. Gasoline is lighter than water. If you poured water into the tank of gasoline, the water would sink to the bottom of the tank. The gasoline would float on top of the water on the fire and flow over the edge of the tank. Then the fire would spread. Gasoline fires should be put out with sand or with chemicals of some kind, such as that used in some fire extinguishers(灭火器).

1. People often put out burning cigarettes by stepping on them. This is because        .

A. the burning cigarettes are too hot to touch

B. it helps to stop smoking

C. it shuts off the air and makes the fire go out

2. According to paragraph 2, what will happen to the water if it is poured on the fire?

A. Some of the water will turn into steam and keep air from the fire.

B. Most of the water will flow away.

C. The water will be absorbed by the fire.

3. Gasoline fire should be put out         .

A. with hot wate

B. with nothing but sand

C. with sand or chemicals