阅读理解。从ABCD中选择合适的句子填入短文1-4中，然后为第5题选择正确答案。
Fire can help people in many ways. 1.________ Fire can heat water, warm houses, give light and cook. But
fire can burn things, too. It can burn trees, houses, animals or people. Sometimes big fire can burn forests.
2.________ But there are many interesting stories about the first time a man or a woman started a fire. One
story from Australia tells about a man very, very long time ago. He went up to the sun by a rope and brought fire
down.
Today people know how to make a fire with matches. Children sometimes like to play with them. But
matches can be very dangerous. One match can burn a piece of paper, and then it might burn a house. A small
fire can become a big fire very fast. Fire kills many people every year. So you must be careful with matches.
3._______. Fires need oxygen (氧气). Without oxygen they will die. Cover a fire with water, sand or sometimes
with your coat. This keeps the air away from a fire and kills it. 4._______. Be careless with fire, and it will burn
you.
A. You should also learn to put out fires.
B. Be careful with fire, and it will help you.
C. Nobody knows for sure how people began to use fire.
D. But it can be very dangerous.
5. Which of the following is the main idea of this passage?
[ ]
A. Fire can help people in many ways.
B. Fire can be both helpful and dangerous.
C. Fire can burn things and people.
D. We must be careful with matches.