Which routing protocol uses hop count as its primary metric?

Correct answer: RIP (Routing Information Protocol)

Option B is correct because RIP (Routing Information Protocol) uses hop count as its sole routing metric, with a maximum hop count of 15, making 16 hops unreachable, which is why RIP is suited only for small networks. Option A is incorrect because EIGRP uses a composite metric that combines bandwidth and delay by default, and optionally reliability and load, rather than simple hop count. Option C is incorrect because BGP is a path-vector protocol that uses path attributes and policies, such as AS path length and local preference, rather than a simple hop count metric. Option D is incorrect because OSPF is a link-state protocol that uses cost based on interface bandwidth as its metric, not hop count, enabling it to select more optimal paths in larger networks.