I travel to the Binhai NewArea by light railway every day,____ do many businessmen who live in

downtown Tianjin.      [ ]

A. as          

B. which      

C. when

D. though

将烧红至约摄氏800度的中碳钢料随即快速冷却，这种处理方法称（）。

A.淬火

B.回火

C.退火

D.调质