PIM BSR is the best final design action because the source uses group 239.1.1.1, which is an administratively scoped ASM multicast group, and dense mode is not allowed. In PIM sparse mode, ASM groups require a rendezvous point so receivers can join the shared tree and sources can register. PIM SSM is not the right match for 239.1.1.1 because SSM normally uses the 232.0.0.0/8 group range and requires receivers to know the source address. Auto-RP can distribute RP information, but traditional Auto-RP discovery relies on multicast groups that often require sparse-dense behavior, which conflicts with the requirement that dense mode is not allowed. BSR is the standards-based PIM mechanism for dynamic RP discovery in sparse-mode networks and avoids static RP configuration on every router. Anycast RP is an RP redundancy design but still requires RP discovery or static RP configuration. Reference topics: PIM sparse mode, Bootstrap Router, ASM, RP discovery, administratively scoped multicast.