1 and 5 graph 2 digraph 6 mixed 3 directed 7 pairwise 9 set 10 undirected 11 vertices 12 4 edges 8 preceding (a) A graph is a way of representing relationships that exist between pairs of objects. That is, a/an is a set of objects, called them, called (b) Viewed abstractly, a/an, together with a collection of_ connections between G is simply a set V of _ and a collection E of pairs of vertices Thus, a graph is a way of representing connections or relationships between pairs of objects from some V. from V, called (c) Edges in a graph are either directed or undirected. An edge (u,v) is said to be the pair (u,v) is ordered, with u v. An edge (u,v) is said to be _ ordered. (d) If all the edges in a graph are undirected, then we say the graph is a/an directed graph, also called a is a graph whose edges are all directed and undirected edges is often called a/an graph can be converted into a directed edges (u,v). (v,u). from u to v if if the pair (u,v) is not graph. Likewise, a A graph that has both graph. Note that an undirected or mixed graph by replacing every undirected edge (u,v) by the pair of