— Liu Yi, do you miss your parents? I hear that you go back home once every month.

— Of course. You know this is the first time I _____ in the dormitory at school, far away from my

     hometown, Luoyang. [ ]

A. have stayed

B. stayed

C. stay

D. am staying

焊接方法中，气焊主要应用于（）。

A．构件变形的火焰矫正

B．低熔点材料(有色金属及其合金)的焊接

C．碳钢、不锈钢、铸铁、铜、铝、镍及合金的焊接

D．化学活泼性强的有色金属、不锈钢、耐热钢等和各种合金