单项选择题
What will significantly degrade DSL performance， regardless of DSL rate or line length？ （）
A.Microliters installed between a telephone and shared line B.POTS splitters at the subscriber’s end of the DSL line C.POTS splitters at the telco CO D.None of the other alternatives apply
单项选择题 ATMcarriesIPandPPPinformationwithATMcells.WhatATMadaptationLayerisusedwhenanATMcellcarriesIPpacketsandPPPframes？（）
多项选择题 WhichtwoofthefollowingaredesignatedfieldsforMACtunnelingprotocol（802.1ah）？（）
单项选择题 ASuccessoris（）.
