A.產(chǎn)品觀念 B.生產(chǎn)觀念 C.市場營銷觀念 D.推銷觀念
A.17910 B.17900 C.17920 D.17930
A.物理層 B.數(shù)據(jù)鏈路層 C.網(wǎng)絡(luò)層 D.傳輸層