Why should a Route Reflector be used in a BGP environment?

Why should a Route Reflector be used in a BGP environment?

A.
Route Reflector is used to overcome issues of split-horizon within BGP.

B.
Route Reflector is used to reduce the number of External BGP peers by allowing updates to reflect without the need to be fully meshed.

C.
Route Reflector is used to allow the router to reflect updates from one Internal BGP speaker to another without the need to be fully meshed.

D.
Route Reflector is used to divide Autonomous Systems into mini-Autonomous Systems, allowing the reduction in the number of peers.