Solution for Section 11.5 Question 1

1. Recall that a graph is called a tree if, and only if, it is circuit-free and connected.

Graph (I) is a tree.
Graph (II) is not a tree since it is not connected (it is forest).
Graph (III) is a tree.
Graph (IV) is not a tree since it contains a circuit.
Graph (V) is a tree.
Graph (VI) is not a tree since it contains a circuit.

Back to Section 11.5