What is the proper configuration to enable route reflector redundancy?

A.
To avoid a single point of failure, IBGP full mesh can be used between all the clients in a cluster.

B.
To avoid a single point of failure, a route reflector client can have IBGP sessions to more than one route reflector within the cluster.

C.
To avoid a single point of failure, a route reflector client can have IBGP sessions to other clients in another cluster.

D.
To avoid a single point of failure, a route reflector client have IBGP sessions to other route reflectors in another cluster.

E.
To avoid a single point of failure, a route reflector client can have IBGP sessions to other route reflectors and other clients in another cluster.