What is one of the reasons that custom QoS ACLs are recommended over automatic QoS when configuring

A. 79xx IP phones do not automatically mark voice packets with non-zero DSCP values.

B. 79xx IP phones do not mark protocol packets such as DHCP, DNS, or TFTP with non-zero DSCP values.

C. 79xx IP phones do not mark voice packets with optimal DSCP values.

D. 79xx IP phones use a custom protocol to communicate CDP information to the switch.