Which statement is correct about AAR?

Which statement is correct about AAR?
A. The end users sees, “Network Congestion Rerouting?” but AAR is otherwise transparent to the end user and works without user intervention.
B. AAR will display “not enough bandwidth” on the IP phone while it reroutes the call.
C. AAR allows calls to be rerouted because of insufficient Cisco Unified Border Element controlled bandwidth to an ITSP.
D. AAR allows calls to be rerouted due to insufficient gatekeeper controlled IP WAN bandwidth.