单选题 Fire can help people in many ways. But it can be very dangerous. 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 fires can burn forests.
Nobody knows for sure how people began to use fire. 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 (绳子)and brought fire down.
Today people know bow to make a fire with matches (火柴). 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. You should also learn to put out fires. 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. Be careful with fire, and it will help you. Be careless with fire, and it will burn you.

单选题 How did people begin to use fire?

【正确答案】 D

【答案解析】[解析] 第二段第一句：“Nobody knows for sure how people began to use fire. ”
事实细节题。根据定位句可知，人们是如何开始使用火的根本就没有人知道。故选D。

单选题 Children mustn"t play with matches because ______.

单选题 When you are going to put out a fire, you ______.

【正确答案】 B

【答案解析】[解析] 第三段第九、十句：“Fires need oxygen (氧气). Without oxygen they will die. ”
事实细节题。根据定位句可知，火燃烧需要氧气，没有氧气它们就会熄灭，所以可以通过使用隔绝空气的方法灭火。故选B。

单选题 We must be careful with fire, or it ______.

单选题 Which of the following is the main idea of this passage?

【正确答案】 B

【答案解析】[解析] 全文。
推理判断题。通读全文可知，本文主要讲述的是火的两面性。火在很多方面可以帮到人们，但同时也会酿成很多灾难。故选B。