Teaching aim: Deal with language points
1. Suddenly, by the light of the lightening, we saw something in the middle of the river. 借着闪电的光亮，我们看到河中央有东西。
by +n./ doing表示“通过某种行为或手段而达到某一目的”。一般在句中作状语。
He found his way by the light of the moon.他借助月光找到了路。
He made a living by writing. 他靠写作为生。
He has improved his English _____ practicing speaking to any foreigner he met.
他遇到外国人就交谈，通过这种练习，他的英语口语已有很大提高。
