1. A bird had snatched up the snake from the ground and then dropped it on to the wires.
一只鸟把蛇从地上抓起来，然后把它扔到了电线上。
知识点：辨析drop，fell:
1) drop v.丢在，降落(主动)；drop n.水珠；[复]眼药水，滴剂
2) fell v.掉下，坠落(被动)；falln.秋天；瀑布(=waterfall)
2. Since then, they have been trying to find out how the fire began.
从那时起，他们一直试图找出起火的原因。
知识点：辨析：begin, start
begin强调从零开始，反义词是end。
start常常是指中断后又开始，反义词是stop。
3. In this way, he was able to solve the mystery.
就这样，他解开了起火之谜。
知识点：was able to solve the mystery = could solve the mystery
4. Forest fires are often caused by broken glass or by cigarette ends which people carelessly throw away.
森林火灾时常由破碎的玻璃渣子或人们随手扔掉的烟头引起。
知识点1：本句中which引导定语从句。
知识点2：broken过去分词作定语，修饰glass。因为碎玻璃可以引起光的折射从而导致火灾的发生。
