18. Suppose we run Dijkstra's single-source shortest-path algorithm on the following weighted directed graph with vertex a as the source. In what order do the nodes get included into the set of verticcs for which the shortest path distances are finalized?(A) a, b, c, d, e,f (B) a, b, c,f, d,e (C) a, b, c, f,e, d (D) a, b, e, c, f, d