Question

Which of the following graphs is/are planar? (see Figure)

• A. G1 only
• B. G1 and G2
• C. G2 only
• D. G2 and G3

Answer 1

The correct option is C G2 only

G1:

$G_{1}is{k}_{3,3}$ which is a well-known non-planar graph.

G2:

Graph $G_2$ is isomorphic to the following graph:


The above graph is planar. So $G_2$ is planar.

G3:

$G_3$ is isomorphic to $K_{3,3}$ which is well known non-planar graph. Therefore, $G_3$ is a non-planar graph.