Mr. Brown is an experienced doctor. He is always         when faced with emergency.

A．as poor as a church mouse

B．as busy as a bee

C．as cool as a cucumber

D．as strong as a horse

工业区位理论的奠基人韦伯认为，工业产品的（）最低点是工业企业选址的理想区位。

A.原料成本

B.生产成本

C.运输成本

D.销售成本