2021-015

Which of the following 4 graphs can be transformed into a bipartite graph by removing one or zero edges?
 

1)

2)

3)

4)

Choose one of the following alternatives that represents the correct answer:

1. 1 and 2.
2. 2 and 4.
3. 3 and 4.
4. 1, 3 and 4.
5. None of the above.

Original idea by: Adolfo Schneider