______ we all know,air is gas.A、As B、Which C、That D、What

问题描述:

______ we all know,air is gas.A、As B、Which C、That D、What

a

选A
如果是C选项:We all know that air is gas.
如果是D选项:What we all know is that air is gas.
至于B选项放哪里都不对

A.