单项选择题 Refer to the exhibit.  What is the effect when the switchport priority extend cos 3 command is  configured on the switch port interface connected to the IP phone？（）

单项选择题 Refer to the exhibit.  Which Catalyst switch interface command would be used to cause the switch  to instruct the phone to override the incoming CoS from the PC before forwarding the packet to the  switch？（）

多项选择题 You have configured voice VLANs on Catalyst switch R1.  Which two statements are true about the  operation of voice VLANs on this device？ （）