by many years 和 for many years区别

问题描述:

by many years 和 for many years区别
总是有些题目把他俩拿来对比,总是搞错,郁闷阿,查字典也查不出来

many years before 用于过去的过去(过去完成时),有对比关系
many years ago表过去(一般过去时)