— Have you been to the Great Wall?

—Perhaps not in my memory. ________, it might have been during my early childhood.

A．If any

B．If so

C．If ever

D．If not

根据GB5185标准的规定，“SAW121”代表（）。

A、丝极埋弧焊

B、等离子弧焊

C、熔化极惰性气体保护焊

D、钨极氩弧焊