单项选择题 You review the Failed Attempts logs on an AAA server and find： "unknown network access servererror."  Which failure could produce this error？（）

单项选择题 You are using ADU and are authenticated and associated to an access point. However， you are unable to obtain an IP address. Which of these has caused this problem？（）

单项选择题 You are configuring a wireless LAN controller for QoS. Which 802.11e user priority tag should you apply to voice applications？（）