This graph has a circuit. Therefore, this graph is not a tree.
Work Step by Step
For any two vertices in a graph, if there is at least one path which has these two vertices as endpoints, then the graph is connected. A tree is a graph that is connected and does not have any circuits. In this graph, the path A,B,C,D,E,A is a circuit since it starts and ends at the same vertex. This graph has a circuit. Therefore, this graph is not a tree.