A tunnel is configured between R3 to R4 sourced with their loopback interfaces. The ip pim sparse-dense mode command is configured on the tunnel interfaces and multicast-routing is enabled on R3 and R4. The IP backbone is not configured for multicast routing. The RPF check has failed toward the multicast source. Which two conditions could have caused the failure? (Choose two.)
A. The route back to the RP is through a different interface than tunnel 0.
B. The backbone devices can only route unicast traffic.
C. The route back to the RP is through the same tunnel interface.
D. A static route that points the RP to GigabitEthernet1/0 is configured.