fall on + 日期,地点,fall用作动词.
eg: Valentine's Day falls on February 14th.
He fell on the playground.
fall in + 温度、价格、成绩等（in后加某方面）,fall多作名词.
eg:There is a fall in temperature.
词组：fall in love with sb.等
fall on + 日期,地点,fall用作动词.
eg: Valentine's Day falls on February 14th.
He fell on the playground.
fall in + 温度、价格、成绩等（in后加某方面）,fall多作名词.
eg:There is a fall in temperature.
词组：fall in love with sb.等