The correct answer is OSPF (Open Shortest Path First). OSPF is a link-state routing protocol known for its fast convergence and use of the Dijkstra algorithm to calculate the shortest loop-free path. It efficiently scales to large enterprise networks and avoids routing loops by maintaining a complete topology map.

A . BGP is primarily an external routing protocol used between ISPs, not internal.

B . STP is not a routing protocol; it prevents loops at Layer 2.

D . RIP is an older distance-vector protocol with slower convergence and a maximum hop limit of 15.

OSPF's design makes it the preferred internal gateway protocol (IGP) for medium-to-large organizations requiring speed and loop-free reliability.

Reference (CompTIA Network+ N10-009):

Domain: Networking Concepts --- IGPs, OSPF, routing protocols.