The ip pim autorp listener command is used to do which of these?

A.
enable a Cisco router to "passively" listen to Auto-RP packets without the router actively sending or forwarding any of the packets

B.
allow Auto-RP packets in groups 224.0.1.39 and 224.0.1.40 to be flooded in dense mode out interfaces configured with the ip pim sparse-mode command

C.
enable the use of Auto-RP on a router

D.
configure the router as an Auto-RP mapping agent

Explanation:
The IP Pim autorp listener allows the Group 224.0.0.39 & 224.0.0.40 to be densed flooded.
As the RP announces 224.0.0.39 to the mapping agent and the mapping agent announces 224.0.0.40 to all routers part of the group.
where it can be applied:
It can be applied when Dense mode is not configured, for example if you have Sparse-mode Multicast Network, and you need not to statically define your RP or use Autorp.