Correct Answer: DTo ensure optimal routing within a hierarchical OSPF network, particularly when dealing with the backbone Area 0 and other OSPF areas, it is crucial to have all backbone links correctly assigned to Area 0. In this scenario, the link dedicated to VLAN 1000, subnet 10.0.0.0/30, which is intended for dedicated high-speed traffic, should be part of Area 0. This ensures that traffic between switches using this link is routed optimally through the backbone area, avoiding any sub-optimal paths. Therefore, making sure that OSPF is enabled in Area 0 on VLAN 1000 on both Switch-1 and Switch-2 is the appropriate solution.