Which two statements are true about the rendezvous poin t (RP) in a multicast network?（）

• 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 Protocol 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.