Which event will cause R2 to establish the (S,G) state for VNI 5100 using R1 as the multicast source?

Referring to the exhibit, R1 and R2 are QFX5100s and are acting as VXLAN Layer 2 Gateways for VLAN 100 using PIM-SM signaling. R2 currently has only the (*.G) state established for VNI 5100.

Which event will cause R2 to establish the (S,G) state for VNI 5100 using R1 as the multicast source?
A . when R1 receives a known unicast Ethernet frame from Host A
B . when R2 receives broadcast, multicast, or unknown unicast from Host A
C . when R2’s VNI 5100 configuration is committed
D . when R2 first learns the MAC address of a locally attached host

Answer: A