将金属零件放在很浓的碱或氧化剂溶液中加热氧化,使其表面生成一层四氧化三铁薄膜的热处理过程为().
A.调质
B.渗碳
C.氮化
D.发黑
参考答案:D
Recently people care more about the safety of . Everyone wants to eat healthily.
A. foods B. clothes C. buildings