Which three statements about BGP confederation and route reflectors are true？ （）

• A、Clusters are used in confederation schemes to avoid loops.
• B、BGP network can have a confederation within a route reflector area.
• C、An internal BGP network cannot have a route reflector within a confederation.
• D、An internal BGP network can have a route reflector within a confederation.
• E、Clusters are used in route reflector schemes to avoid loops.
• F、BGP network cannot have a confederation within a route reflector area.