What is the purpose of IGMP in a multicast implementation?

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 CareerCert.blogspot.com

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