Which one of these statements best describes the challenge the designer when dealing with IP routing?

A.
OSPF supports fast convergence does not require periodic routing table updates, so the optional network design is best simplified with the network as a single backbone area.

B.
Manual summarization is limited to ABRs and ASBRs, therefore the designer must pay strict attention to the EIGRP topology.

C.
EIGRP, as a proprietary protocol, has special challenges when dealing with networks deployed with IPv6.

D.
Effective scalability with OSPF requires the designer to pay strict attention to the hierarchical network structure, localizing topology changes.

Explanation:
OSPF demands modular design, multiple areas for functioning optimally. Link: http://www.cisco.com/en/US/tech/tk365/technologies_white_paper09186a0080094e9e.shtml