Router R5 receives four route updates for the same prefix. Which of the four routes will be installed in R5's routing table?

In routing protocols, when a router receives multiple updates for the same prefix, it applies certain rules to determine which route to install in its routing table. The key factors typically include the administrative distance, metric values, and the specific routing protocol used.

In this case, if route updates are being considered, one likely reason for D being the correct answer is that it has the most preferred administrative distance or the best metric among the received routes. Administrative distance is a value that routers use to determine the trustworthiness of the route source; lower values indicate more reliable sources. If the route from router R4 offers the best metric (e.g., shortest path) and a lower administrative distance than those from R1, R2, and R3, then it would be the route that gets installed in R5's routing table.

In routing, the principle of using the best route applies heavily when multiple routes exist for the same destination. Therefore, if R4's route is the most efficient (with a better metric or lower administrative distance), it becomes the selected route installed in the routing table of R5.