They were students when they were in their( )为什么是twenties?

问题描述:

They were students when they were in their( )
为什么是twenties?

同意楼上观点,难道你想写twenty ??

in sb's twenties表示在某人二十多岁时
表示几十岁时的用法,比如三十多岁就说thirties