RTA Is a Source's DR and RTB Is an RP

RTA is a source's DR and RTB is an RP. A multicast source sends multicast data to RTA but RTB cannot find any information about the multicast source (registered by using the PIM Register message) . Why? (Choose three.)

A) RTB has no unicast routes to RTA.
B) RTA fails to learn RP information.
C) RTA has no unicast routes to RTB.
D) The RP learned by RTA is not RTB.