—Where have you been recently?

—I ______ in Hangzhou on business for a week last month.[ ]

A. have been    

B. was            

C. had been          

D. had gone

牌号Q235－A·F钢的“F”是代表（）的符号。

A.质量等级

B.脱氧方式

C.耐热程度

D.产品用途