Which three statements are true about the voice VLAN feature on a Catalyst 2950 switch？ （Choose  three.）（）  

• A、 The CoS value is trusted for 802.1p or 802.1q tagged traffic.
• B、 The voice VLAN feature is disabled by default.
• C、 The IP phone accepts the priority of all tagged and untagged traffic and sets the CoS value to 4.
• D、 When the voice VLAN feature is enabled， all untagged traffic is sent according to the default CoS priority of the port.
• E、 PortFast is automatically disabled when a voice VLAN is configured.
• F、 The default CoS value for incoming traffic is set to 0.