流动水分点可用来衡量（）特性的指标。
A．一般固体散货
B．易流态化货物
C．具有化学危险的固体散货
D．包装危险性货物
参考答案：B
He works as an engineer now, but he _____ on a farm for three years.
A．has worked
B．worked
C．was working
D．had worked
物料提升机的基础浇注C20混凝土，厚度不得少于（）。
A.150mm
B.250mm
C.250mm
D.300mm
