Which three statements are true about IP multicast configuration? (Choose three.)

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.

Explanation:
If you configure PIM to operate in sparse mode, you must also choose one or more routers
to be rendezvous points (RPs). RPs are used by senders to a multicast group to announce
their existence and by receivers of multicast packets to learn about new senders.
Dense mode interfaces are always added to the table when the multicast routing table is
populated. Sparse mode interfaces are added to the table only when periodic join messages
are received from downstream routers, or there is a directly connected member on the
interface.
In PIM sparse-dense mode, if an RP is not known for a group, the router sends data using
PIM dense mode. However, if the router discovers an RP or you configure an RP statically,
PIM sparse mode takes over.
References:
http://www.cisco.com/en/US/docs/ios/12_3/ipmulti/command/reference/ip3_i2g.html
http://www.juniper.net/techpubs/software/erx/junose53/swconfig-routing-vol1/html/ipmulticast-config15.html