我们班的同学都有一种习惯——进教室先开灯。这种习惯从小学一年级养成,四年级却“退化”了。为什么呢?因为在四年级时我们换了一位新班主任,那就是梁老师。他利用了一节语文课的时间,为我们放了一个宣传片。片子里讲的是,如果人类每人每小时能节约5度电,那么地球上所有人一小时将节约6亿5千万度电,如果人类一直保持下去,那么地球 Classmates have a habit in our class - turn on the light in the classroom. This habit from the first grade primary school to develop, but the fourth grade “degradation ”. Why? Because in the fourth grade when we changed a new class teacher, that is Liang teacher. He took a Chinese class time and put a trailer for us. The movie tells us that if humankind can save 5 kWh per hour per person, then every hour on earth would save 650 million kilowatt hours. If mankind persists, then Earth