Which two statements about RPF checks in Multicast Source Discovery Protocol （MSDP） are true？（）

• A、It prevents message looping， Session Advertisement （SA）messages must be RPF checked
• B、RPF check should be done against the route to the source S of the corresponding PIM-SM domain
• C、RPF check should be done against the route to the Rendez-vous Point of the corresponding PIM-SM domain，which originated the SA
• D、RPF checking Session Advertisement （SA） messages will cause message looping