A.物理層 B.數(shù)據(jù)鏈路層 C.傳輸層 D.網(wǎng)絡層
A.4 B.16 C.32 D.64
A.255.255.255.192 B.255.255.255.224 C.255.255.255.240 D.255.255.255.248