Chapter 14 - Graph Theory - 14.4 Trees - Exercise Set 14.4 - Page 931: 31

We can make a spanning tree with the edges AB, AC, and CD. We can make a spanning tree with the edges AB, AD, and CD. We can make a spanning tree with the edges BC, AC, and AD. We can make a spanning tree with the edges BC, CD, and AD.

The original graph has 4 vertices and 5 edges. If a tree has 4 vertices, then it must have exactly 3 edges. To make a spanning tree from the original graph, we need to choose 3 edges from the original graph. We can make a spanning tree with the edges AB, AC, and CD. We can make a spanning tree with the edges AB, AD, and CD. We can make a spanning tree with the edges BC, AC, and AD. We can make a spanning tree with the edges BC, CD, and AD.