But all this does is to lower you to that same negative level.中的does是什么用法?

题目

But all this does is to lower you to that same negative level.中的does是什么用法?

答案

分析一下句子,你就明白了：
But all（主语） this does（省略了引导词的定语从句,修饰all） is（谓语） to lower you to that same negative level（不定式短语作表语）.
具体的翻译要根据上下文了.