Use things for as long as possible.为什么这里要加for?

题目

Use things for as long as possible.为什么这里要加for?
意思是这里for的作用是什么.

答案

后面接一段时间的话前面要用介词for
如：我在成都呆过两年.
I had been in Chengdu for 2 years.
Use things for as long as possible.
as long as possible 表示“尽可能长的时间”