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.