Which of these are true of breadth$-$first search?

A: Breadth$-$first search keeps its set of previously visited nodes in a stack.

B: Breadth$-$first search is guaranteed to have the shortest possible run$-$time

in finding a path, if one exists.

C: Breadth$-$first search only works on directed graphs; for an undirected

graph, you have to use depth$-$first search.

D: Breadth$-$first search is guaranteed to find a shortest path in terms

of total number of hops in your graph.