Liu Fang is a company CEO now, but she ____ as a teacher in a middle school for three years.

A．worked

B．has worked

C．works

D．had worked

建筑企业的（）一级，是材料供、管、用的基层单位它的材料工作的重点是管和用。

A.工区

B.项目部

C.施工队

D.生产工人