单项选择题
A.合金结构钢B.合金工具钢C.耐热钢D.不锈钢
A.< 0.25%B.0.1~0.45%C.0.25~0.5%D.0.35~0.70%
A.4~5B.1~3C.7~14D.5~7
A.0.1~0.25%B.0.25%~0.5%C.0.25%~0.6%D.0.45%~0.75%
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