First listen and then answer the question.
    听录音，然后回答以下问题。
    What caused the fire?
    
    

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 fireman 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  adj. 带电的，充电的
fireman  n. 消防队员
cause  v. 引起； n. 原因
examine  v. 检查
accidentally  adv. 意外地，偶然地
remains  n. 尸体，残骸
wire  n. 电线
volt  n. 伏特（电压单位）
power line  电力线
solve  v. 解决
mystery  n. 谜
snatch  v. 抓住
spark  n. 电火花

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。