All the students will remember the day on （B which） we had the first heavy snow this year.
全体学生都会记得今年第一次下大雪的那天.
括号中要填定语从句的引导词.what是不能用于定语从句的,首先排除D.when相当于介词加引导词,前面不能用介词on了,所以C项也错.that是不能用于介词之后,也错.只有which前可用介词,代替先行词the day.