Which two statements are true about the function of CAC？ （）

A. CAC provides guaranteed voice quality on a link.
B. CAC artificially limits the number of concurrent voice calls.
CAC is used to control the amount of bandwidth that is taken by a call on a link.
D. CAC prevents oversubscription of WAN resources that is caused by too much voice traffic.
E. CAC allows an unlimited number of voice calls while severely restricting， if necessary， other forms of traffic.
F. CAC solves voice congestion problems by using QoS to give priority to UDP traffic.