A.passed by the AP to its connected switch and then forwarded directly to the connected router，which  creates an MGID table entry
B.passed by the AP to the WLAN controller and then forwarded to the source PIM-enabled router，which  creates an MGID table entry
C.passed by the AP to the WLAN controller， which creates an MGID table entry before forwarding to the  directly connected PIM-enabled router
D.passed by the AP to its connected switch and then forwarded to the rendezvous point router，which  creates an MGID table entry

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