单项选择题
A.20CrMnTi B.45 C.08 D.GCr15
A.10Cr17 B.12Cr18Ni9 C.68Cr17 D.GCr15
A.0.045% B.0.45% C.4.5% D.45%
A.45 B.60 C.75 D.85
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