Which statement correctly describes how PIM forwards multicast traffic?

PIM sparse mode (PIM-SM) operates on a "pull" model, meaning receivers explicitly request multicast traffic. This is achieved when a receiver joins a multicast group, and its local router sends a PIM Join/Prune message towards the Rendezvous Point (RP) to register interest. The RP then pulls traffic from the source. PIM dense mode (PIM-DM) uses a "push" or flood-and-prune model, where multicast traffic is initially flooded to all routers in the domain and then pruned from branches without active receivers. While PIM-SM does involve receivers registering interest, the core mechanism for traffic delivery is the pull model, not simply registration.