单项选择题
A.0.0008% B.0.0218% C.0.77% D.2.11%
A.0.77%~2.11% B.0.0008%~0.0218% C.0.0218%~0.77% D.0~0.0218%
A.珠光体+铁素体 B.铁素体+奥氏体 C.铁素体+渗碳体 D.珠光体+渗碳体