单项选择题
A.0.10%〜0.30%B.0.30%〜0.50%C.0.50%〜0.80%D.0.80%〜0.90%
A.0.1%-0.2%B.0.2%-0.45%C.0.45%-0.6%D.0.6%-0.8%
A.稳定剂B.脱氧剂C.覆盖剂D.脱硫剂