单项选择题
A.1 B.2 C.3 D.4
A.3 B.4 C.5 D.6
A.30～35HRC B.40～50HRC C.62～72HRC D.80～90HRC
A.0.2～0.16 B.0.33～0.25 C.0.77～0.42 D.2.3～0.83
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