A.>2.11g/cm3 B.<2.11g/cm3 C.≤4.5g/cm3 D.<2.5g/cm3
A.>2.11% B.<2.11% C.>2.5% D.<2.5%
A.碳素鋼 B.鎂合金 C.球墨鑄鐵 D.合金鋼