Which mechanism would you recommend to ensure WAE availability and failover if a WAE fails?

Your customer is using PBR as the interception method on its routers. Which mechanism would you recommend to ensure WAE availability and failover if a WAE fails?

A.
enable NetFlow to track WAE appliances

B.
enable IP SLAs to track WAE appliances

C.
nothing, PBR automatically tracks WAE appliances

D.
nothing, PBR does not support the tracking of WAE appliances