以下句子中,which后为什么要的是has而不是have?which指代的究竟是什么?

问题描述:

以下句子中,which后为什么要的是has而不是have?which指代的究竟是什么?
We,post—90's generation,are living in a society full of fierce competitions,and developing our special manners and values,which has raised people's concern.

which代指前面的"We,post—90's generation,are living in a society full of fierce competitions,and developing our special manners and values",相当于代替前面句子的意思,只能用单数.