When configuring BGP on routers within a transit AS, under what circumstances should BGP synchronization be enabled?
A. when a full-mesh iBGP is used
B. when route reflectors are used
C. when BGP confederation is used
D. when redistributing the BGP routes into IGP
E. when redistributing the IGP routes into BGP
F. when the edge routers are using the BGP next-hop self option
