What are three methods that may be use d to allow a switch to determine which ports to forward IP multicast messages to?（）

A. Sparse mode multicast uses a pull model to send multicast traffic to where it is requested
B. Dense mode multicast uses a push model to flood traffic throughout the network and then prunes the unwanted traffic
C. Dense mode multicast requires explicit join messa ges from their members
D. Sparse mode uses reverse path forwarding (RPF) to prune off redundant flows
E. The primary use of sparse mode multicast is for test labs and router performance testing

A. The multicast sources must register with the RP to form the multicast distribution tree
B. An RP is required only in networks running Protocol Independent Multicast dense mode ( PIM DM)
C. The multicast receivers must register with the RP to form the multicast distribution tree
D. An RP is required only in networks running Protocol Independent Multicast sparse mode (PIM SM)
E. An RP is required only in networks running Pro tocol Independent Multicast sparse - dense mode (PIM - SDM)
F. To form the multicast distribution tree, the multicast sources register with and the receivers join the RP

A. both routers R1 and R2
B. router R1
C. router R2
D. none of the routers since they are not configured with static RP