Chapter 14 - Graph Theory - 14.1 Graphs, Paths, and Circuits - Exercise Set 14.1 - Page 902: 49

We can draw a graph with four vertices with edges AB, AC, BD, and CD. Then the degree of each vertex is 2, so each vertex is an even vertex. Since each vertex is even, this is a graph with four even vertices.

The degree of a vertex is the number of edges connected to the vertex. If the degree of a vertex is an even number, then the vertex is an even vertex. We can draw a graph with four vertices with edges AB, AC, BD, and CD. Then the degree of each vertex is 2, so each vertex is an even vertex. Since each vertex is even, this is a graph with four even vertices.