Correct Answer: D
When the link between R2 and R3 is restored, the path reverts back to R1-R2-R3 because this was the previous best path. This is because OSPF uses the Dijkstra algorithm to calculate the shortest path tree (SPT) and the path with the lowest cost is chosen as the best path. In this case, the cost of the path R1-R2-R3 is lower than the cost of the path R1-R4-R5-R3, so the path R1-R2-R3 is chosen as the best path. OSPF also has a preference order for different types of routes, such as intra-area, inter-area, external type 1, external type 2, NSSA type 1, and NSSA type 2. However, this preference order only applies when OSPF has to choose between routes of different types to the same destination. In this scenario, both paths are external type 2 routes, so the preference order does not affect the path selection