An Algorithm That Uses a Stack to Implement a Nonrecursive

Multiple Choice

An algorithm that uses a stack to implement a nonrecursive solution to the HPAir problem reaches the conclusion that there is no path from an origin city to a destination city only after ______.

A) the algorithm has backtracked to the origin
B) the algorithm has backtracked to the origin and there remain no unvisited cities to fly to from the origin
C) the algorithm has reached a city and there remain no unvisited cities to fly to from that city
D) the algorithm has reached the destination and there remain no unvisited cities to fly to from the destination