Which three components should you implement?

You have a Microsoft I earns deployment and an existing telephony solution that provides PSTN capability to on premises third-party PBX systems in two separate locations.

You need to implement a redundant PSTN solution for Microsoft Teams Phone. The solution must use the existing telephony earner services. The solution must ensure that outbound calls can be made if a component fails.

Which three components should you implement? Each correct answer presents part of the solution. NOTE: Each correct selection is worth one point
A . highly available Session Border Controllers (SBCs)
B . calling policies
C . PSTN usages
D . voice routing policies
E . tenant dial plans

Answer: C,D,E