The route-reflector design should make R2 a client of R1 and R4, and R5 a client of R3 and R4. The requirement states that the route reflector must have direct physical connections to the core routers R3 and R4, must avoid a single point of failure, and must account for high utilization on the R2-to-R1 link. In BGP route-reflector design, clients peer with redundant route reflectors so they can continue receiving reflected routes if one route reflector or path fails. Placing R5 as a client of R3 and R4 satisfies the direct-core requirement and provides redundant reflection through the core. Placing R2 as a client of R1 and R4 provides redundancy while reducing dependence on the heavily utilized R2-to-R1 link by including R4 as an alternate reflector. Making a router a client of two reflectors is a standard design technique for route-reflector high availability. The other combinations either fail the direct-core requirement, do not provide balanced redundancy, or keep traffic tied to the congested link. Reference topics: BGP route reflectors, client redundancy, iBGP scaling, route-reflector placement, core resiliency.