问题：

[多选] 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.
C . 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.