Which solution quickly allows this multicast traffic to go through while allowing for future scalability?

Refer to the exhibit.

This enterprise customer wants to stream one-way video from their head office to eight branch offices using multicast. Their current service provider provides a Layer 3 VPN solution and manages the CE routers, but they do not currently support multicast.

Which solution quickly allows this multicast traffic to go through while allowing for future scalability?
A . Enable a GRE tunnel between nodes C2 and C4
B . Enable a GRE tunnel between nodes C1 and C4
C . Implement hub and spoke MPLS VPN over DMVPN (also known as 2547oDMVPN) between CE1 and CE2
D . Enable a GRE tunnel between nodes CE1 and CE2
E . The service provider must provide a Draft Rosen solution to enable a GRE tunnel between nodes PE1 and PE2

Answer: A