新概念英语第二册 Lesson 53 · 语法精读与固定搭配分类
本课是一则「蛇引起森林大火」的科普小小说。语言点集中在 被动语态（are caused / was wound）、现在完成进行时 have been trying、以及 in this way、find out、be wound round 等短语；句中还用到 wound 的两种含义。
| 句子 | 语法点 |
|---|---|
| At last firemen have put out a big forest fire in California. | at last 最后，终于 · put out 扑灭（火）· fireman 的复数是 firemen（不规则变化） |
| Since then, they have been trying to find out how the fire began. | 现在完成进行时 have been trying：从那以后一直试图（并持续到现在）· since then 从那时起，与完成时连用 · 宾语从句 how the fire began，作 find out 的宾语 |
| 句子 | 语法点 |
|---|---|
| Forest fires are often caused by broken glass or by cigarette ends which people carelessly throw away. | 被动语态 are caused by：由……引起 · broken glass 碎玻璃 · cigarette ends 烟头 · which people carelessly throw away 是定语从句，修饰 cigarette ends |
| Yesterday the firemen examined the ground carefully, but were not able to find any broken glass. | examine 仔细检查 · be not able to do sth. 未能做某事 · any 用于否定句中 |
| They were also quite sure that a cigarette end did not start the fire. | be quite sure that … 十分肯定…… · 宾语从句 that 引导 · start the fire 引起火灾 |
| 句子 | 语法点 |
|---|---|
| This morning, however, a fireman accidentally discovered the cause. | however 作插入语，表转折 · accidentally 偶然地（accident + -al + -ly）· discover the cause 发现原因 |
| He noticed the remains of a snake which was wound round the electric wires of a 16,000-volt power line. | 被动语态 was wound round：被缠绕在……上 · the remains of a snake 一条蛇的残骸 · a 16,000-volt power line 一条 16,000 伏的高压线 |
| In this way, he was able to solve the mystery. | in this way 就这样 · be able to do 能够做（强调成功）· solve the mystery 解开谜团 |
| 句子 | 语法点 |
|---|---|
| The explanation was simple but very unusual. | explanation 解释（explain 的名词形式）· simple but very unusual 简单却很不寻常，为下面的解释作铺垫 |
| A bird had snatched up the snake from the ground and then dropped it on to the wires. | 过去完成时 had snatched up：先发生的动作 · snatch up 抓起，攫取 · drop sth. on to 把某物丢到……上 |
| The snake then wound itself round the wires. | wind oneself round ＝ 把自身缠绕在……上 · 注意 wind（/waɪnd/ 缠绕）与 wound（/wuːnd/ 伤口）拼写相同、读音不同 |
| When it did so, it sent sparks down to the ground and these immediately started a fire. | do so 代替前面提到的动作（wound itself round the wires）· send … down to 把……送到 · spark 电火花 · 结尾把整条因果链收齐：蛇缠线 → 短路 → 火花落地 → 起火 |
| 短语 | 用法与例句 |
|---|---|
| put out | 扑灭（火）；也可表示「伸出」：put out a big forest fire。 |
| find out | 查明，弄清楚：find out how the fire began。 |
| in this way | 就这样，用这种方法：In this way, he was able to solve the mystery。 |
| be caused by | 由……引起：Forest fires are often caused by broken glass。 |
| be wound round | 被缠绕在……上：a snake which was wound round the electric wires。 |
| power line | 电力线，输电线：the electric wires of a 16,000-volt power line。 |
| hot | 带电的，通电的（本课标题）：Hot snake ＝ 带电的蛇（触电的蛇）。 |