What is correct about IGMP Snooping?

What is correct about IGMP Snooping?
A . Both IGMP & IGMP Snooping can be configured in the same VLAN
B . Port quick leave means that when the switch leaves the IGMP Leave message, it directly deletes the port from the outgoing port list of the corresponding forwarding entry
C . The unknown multicast group dropping function can be enabled on the switch. When the switch receives unknown multicast data packets, it will only forward to its router port and not broadcast in the VLAN.
D . Using the iIGMP Snooping function on the Layer 2 device can establish and maintain multicast forwarding entries at the data link layer, so that multicast data can be forwarded normally at the data link layer

Answer: BC