多项选择题
Which three of these are elements of the Cisco Unified Wireless Network architecture？（）
A.cell phones B.remote access C.mobility services D.network management E.network unification F.network decentralization
单项选择题 WhichoftheseisaLayer2transportarchitecturethatprovidespacket-basedtransmissionoptimizedfordatabasedonadual（counter-rotating）ringtopology？（）
单项选择题 WhichoftheseLayer2accessdesignsdoesnotsupportVLANextensions？（）
单项选择题 For acceptable voice calls, the packet error rate should be less than（）%
