选择题：Which three statements are true about IP multicast configuration?()

A. PIM sparse - dense mode and PIM dense mode require an RP on the network.

B. PIM sparse mode and PIM dense mode require an RP on the network.

C. PIM sparse mode interfaces are always added to the multicast routing table in a router.

D. PIM sparse mode and PIM sparse - dense mode require an RP on the network.

E. PIM dense mode interfaces are always added to the multicast routing table in a router.

F. PIM sparse - dense mode acts as PIM dense mode if an RP is not known.