1. Is the following a graph? Explain.
![1170_Graph.png](https://secure.tutorsglobe.com/CMSImages/1170_Graph.png)
2. The vertices of the following graph are to be colored so that the adjacent vertices will not have the same color. Find the chromatic number of the following graph.
![383_Graph1.png](https://secure.tutorsglobe.com/CMSImages/383_Graph1.png)
3. What is the minimum number of colors required for the following graph so that the adjacent regions with a common boundary other than a point are to have different colors?
![1869_Graph2.png](https://secure.tutorsglobe.com/CMSImages/1869_Graph2.png)