He will be back after two hours

问题描述:

He will be back after two hours
改错,答案是把after改成in,为什么不改成for、by或者during?

in 指在.期间,或在.之内.一般用在将来要发生的事.He will be back in two hours.for 表示所用时间有多长.He stayed at home for two hours.during 表示在.期间,一般用在已经发生的事.He had read 3 books during the...