What is the purpose of the WLC Controller->Multicast->IGMP Timeout feature operating on v5.2?（）

A、to determine if there are more clients that are using the multicast stream

B、to limit the time that a client has to request an IGMP join to the controller multicast group

C、to determine if the multicast router is still alive and responding to multicast clients

D、to remove clients from the multicast group if the multicast traffic exceeds the allotted bandwidth allowed  for multicast clients