单项选择题 A wireless client cannot connect to an 802.11b/g BSS with a b/g wireless carD.The client section of the access point does not list any active WLAN clients. What is a possible reason for this?（）

多项选择题 在应用层的各协议中（）协议提供文件传输服务。

单项选择题 Which parameter can be tuned to affect the selection of a static route as a backup. when a dynamic protocol is also being used？（）