A. Dense mode multicast requires explicit join messages from their members.
B. Dense mode multicast uses a push model to flood traffic throughout the network and then prunes the  unwanted traffic.
C. Sparse mode multicast uses a pull model to send multicast traffic to where it is requested.  
D. Sparse mode uses reverse path forwarding （RPF） to prune off redundant flows.
E. The primary use of sparse mode multicast is for test labs and router performance testing.

A. If a packet is sent to a multicast group address， all members of the multicast group will receive it
B. If a packet is sent to a multicast group address， the multicast frame contains the source multicast  address
C. A router does not have to be a member of a multicast group to receive multicast data.
D. A router does not have to be a member of a multicast group to send to the group.
E. A router must be a member of a multicast group to receive multicast data.
F. A router must be a member of a multicast group to send to the group.