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.