What is the purpose of IGMP in a multicast implementation?（）

A.it is not used in multicast

B.it determines the virtual address group for a multicast destination

C.it dynamically registers individual hosts in a multicast group on a specific LAN

D.it is used on WAN connections to determine the maximum bandwidth of a connection

E.it determines whether Bidirectional PIM or PIM sparse mode will be used for a multicast flow