Choose the true statement regarding QoS pre-classify.（）

• A、QoS pre-classify permits making QoS decisions based on elements from the unencrypted IP packet.
• B、QoS pre-classify is required when encrypting voice.
• C、QoS pre-classify is an advantage to Service Providers transporting encrypted packets.
• D、QoS pre-classify is not designed for IPSec/GRE configurations.