Which two statements are true about Internet Group Management Protocol (IGMP) snooping?（）

• A、IGMP snooping and Cisco Group Membership Protocol (CGMP) can be used simultaneously on a switch.
• B、IGMP snooping a nd Cisco Group Membership Protocol (CGMP) were developed to help Layer 3 switches make intelligent forwarding decisions on their own.
• C、IGMP snooping examines IGMP join/leave messages so that multicast traffic is forwarded only to hosts that sent an IG MP message toward the router.
• D、IGMP snooping is an IP multicast constraining mechanism for Layer 2 switches.
• E、IGMP snooping is enabled with the ip multicast - routing global configuration command.