13.A graph G is an undirected graph with n vertices and each vertex has exactly degree d. Assume n is odd. What can you say about d? a. d must be odd b. d must be even c. d can be odd or evern 14. Given a connected graph of n vertices and m edges, with no self-loops or parallel edges, the minimum and maximum number of edges of the graph is b, n-1= n, then G has a cycle a. Always true b. Sometimes true c. Never true 16. After running DFS on a graph G, how many of the following statements about the edge e-(u -> v) are correct? o e is a tree edge if and only if dd,f f,and while exploring the edge e, vertex v has not been visited yet. e is a forward edge if and only if du dff, and while exploring the o edge e, vertex v has been visited before o e is a back edge if and only if d, d fy o e is a cross edge if and only if d.