单项选择题
A.化学防锈 B.气相防锈 C.喷砂防锈 D.涂油防锈
A.边宽 B.边宽×边厚 C.边宽×边宽 D.边宽×边宽×边厚
A.50W/kg B.360W/kg C.50kg/W D.360kg/W
A.71/4in B.73/4in C.8in D.9in
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