Which of the following pair of angles are vertical angles?

To find out which pair of angles are vertical angles. We must know that:

As for angles I & II, they are not vertical angles. This is because these two angles are adjacent angles.

Similarly, angles II & III and III & IV are not vertical angles for the same reason as above.

Only angles I & III are vertical angles as these angles fulfill the properties mentioned in Step 1. Hence, the answer is D.

Feeling bored of worksheets? Try Zap Zap Math game to find out the secret of people who fall in love with math.