Late _____the afternoon of a cold day in February ,two gentlemen  were sitting Over their wine in a restaurant.

A in  B on  C of  D　at

高碳钢成品P含量偏高的主要原因是（）。

A.吹炼过程不去磷

B.出钢容易回磷

C.熔池不均匀

D.吹炼过程去磷