单项选择题
A.IPv4地址 B.MAC地址 C.主机名 D.任意字符串
A.18.0.0.14 B.18.31.0.14 C.18.240.0.0 D.18.9.0.14
A.255.255.240.16 B.255.255.16.0 C.255.255.255.248.0 D.255.255.240.0