单项选择题
A.154.100.80.128 B.154.100.80.190 C.154.100.80.192 D.154.100.80.254
A.C0 B.C1 C.C2 D.C3
A.255.192.0.0 B.255.240.0.0 C.255.255.240.0 D.255.255.248.0