能够切割金属与金属材料，且能切割大厚工件的切割方法为()。

A.氧熔剂切割 

B.等离子弧切割 

C.碳弧气割 

D.激光切割

I don't know __     now.    [ ]

A. where is he working              

B. where he is working    

C. where did he work                

D. where he worked