First listen and then answer the question.
听录音，然后回答以下问题。
What caused the fire?
英式发音：
美式发音：
At last firemen have put out a big forest fire in California. Since then, they have been trying to find out how the fire began. Forest fires are often caused by broken glass or by cigarette ends which people carelessly throw away. Yesterday the firemen examined the ground carefully, but were not able to find any broken glass. They were also quite sure that a cigarette end did not start the fire. This morning, however, a firemen accidentally discovered the cause. He noticed the remains of a snake which was wound round the electric wires of a 16，000-volt power line. In this way, he was able to solve the mystery. The explanation was simple but very unusual. A bird had snatched up the snake from the ground and then dropped it on to the wires. The snake then wound itself round the wires. When it did so, it sent sparks down to the ground and these immediately started a fire.
New words and expressions 生词和短语hot(title)/hɔt/adj.带电的，充电的
wire(1.9)/'waiə/n.电线
fireman(1.1)/'faiəmən/ n. 消防队员
volt(1.9)/vəult/n.伏特(电压单位)
cause(1.3)/kɔ:z/v.引起；n．原因
powerline(1.9)/'pauə-lain/电力线
examine(1.4)/ig'mæmin/v.检查
solve(1.9)/sɔlv/v.解决
accidentally (1.7)/'æksi'dentli/adv.意外地，偶然地
mystery (1.9)/'mistəri/n.谜
snatch(1.10)/snætʃ/v. 抓住
remains(1.8)/ri'meinz/n.尸体，残骸
spark(1.11)/spa:k/n.电火花
Notes on the text 课文注释
1 at last，最后，终于。
2 they have been trying to find out how the fire began，他们一直试图找出起火的原因。句中短语动词 find out 的宾语是一个从句 how the fire began。
3 broken glass，碎玻璃。
4 cigarette ends，烟头。
5 in this way，就这样。
参考译文
消防队员们终于扑灭了加利福尼亚的一场森林大火。从那时起，他们一直试图找出起火的原因。森林火灾时常由破碎的玻璃或人们随手扔掉的香烟头引起。昨天，消防队员仔细查看了地面，但未能发现碎玻璃。他们还十分肯定火灾也不是由烟头引起的。然而今天上午，一个消防队员偶然发现了起火的原因。他发现了缠绕在16，000伏高压线上的一条死蛇。就这样，他解开了起火之谜。解释很简单，却异乎寻常。一只鸟把蛇从地上抓起来，然后把它扔到了电线上。于是蛇就缠住了几根电线。当它这样做时，把火花送到了地面，这些火花立刻引起了一场大火。
