I’m good ______ old people and I’m good ______ playing the guitar, so I can join you to help them.

A．for, with

B．for, at

C．with, at

D．at, for

阶级产生的直接原因是______。

A．一部分人对另一部分人的暴力掠夺

B．社会产品的分配不均

C．剩余产品的出现

D．生产资料私有制的形成