The correct answer is C.
OBJ-2.2: Route poisoning is a method to prevent a router from sending packets through a route that has become invalid within computer networks. This is achieved by changing the route’s metric to a value that exceeds the maximum allowable hop count so that the route is advertised as unreachable. The Spanning Tree Protocol (STP) is a network protocol that builds a loop-free logical topology for Ethernet networks and operates at layer 2 of the OSI model. The basic function of STP is to prevent bridge loops and the broadcast radiation that results from them. A split-horizon route advertisement is a method of preventing routing loops in distance-vector routing protocols by prohibiting a router from advertising a route back onto the interface from which it was learned. A hold down timer is a function of a router that prevents a route from being updated for a specified length of time (in seconds). A hold down timer allows for the routers in a topology to have sufficient time to reach convergence and be updated when a route fails.