What happens when users at Site B place calls to Site A when the IP WAN is operational?

Refer to the exhibit.

What happens when users at Site B place calls to Site A when the IP WAN is operational?

A.
The calls will always take the IP WAN route.

B.
The calls will always take the PSTN route.

C.
The calls will fail because the destination patterns are identical.

D.
The calls will use round-robin scheduling between the IP WAN and PSTN paths.

E.
The calls will use the IP WAN route unless there is a failure or congestion during which the calls will reroute via the PSTN.

Explanation: