— How do you like your English teacher? 

— He is great. We _____ friends since three years ago. [ ]

A. were

B. have made

C. have been

D. have become

轧后控冷的目的是什么（）

A．使钢易加工

B．钢材易矫直

C．保留位错组态

D．细化晶粒