Refer to the exhibit.

Both WAN routers should run OSPFv2. The requirement explicitly says that the routing protocol must be open standard, provide high availability, and offer fast convergence. OSPF is an open-standard link-state routing protocol and is broadly supported across vendors. It builds a link-state database, calculates best paths with SPF, supports equal-cost multipath, and can be tuned with BFD, SPF throttling, LSA throttling, and hierarchical areas for resilient enterprise WAN designs. EIGRP is fast and operationally efficient in Cisco-only environments, but it is not the best answer when the requirement emphasizes an open-standard routing protocol. Running OSPFv2 on one router and OSPFv3 on another is invalid for a single IPv4 routing design because they would not form the intended common routing domain. Mixing IS-IS and OSPFv3 also fails the requirement for a unified design between the redundant routers. Therefore, both routers should run OSPFv2. Reference topics: OSPFv2, open-standard routing, WAN routing high availability, link-state convergence, ECMP and BFD integration.