If the primary path goes down, what will EIGRP use to reach a destination?

A.
administrative distance

B.
advertised successor

C.
successor

D.
feasible successor

Explanation:
The key to this question is the four terminology about DUAL.
Enhanced Interior Gateway Routing Protocol (EIGRP) is an enhanced distance-vector
protocol based on the diffusing update algorithm (DUAL). It is capable of (conservatively)
finding all loop-free paths to any given destination based on route advertisements from
neighbors. The neighbor (or neighbors) with the best path to a destination is called the
successor. The remaining neighbors with loop-free paths to the destination are called
feasible successors. To reduce traffic load on the network, EIGRP maintains neighbor
relationships and exchanges routing information only as needed, using a query process to
find alternate paths when all loop-free paths to a destination have failed.