Which two statements about voice VLANs are correct？（）

• A、Voice VLANs eliminate the need for QoS configuration
• B、Voice VLANs are used on trunk links to eliminate the need for QoS CoS markings
• C、Voice VLANs are mainly used to reduce the number of access switch ports that are used in the network
• D、Voice VLANs can be configured to forward existing CoS priorities or override them
• E、Voice VLANs are mainly used between access layer switches and distribution layer switches
• F、Voice VLANs can be configured on Layer 2 ports only