Answer: B. Volatile organic compounds and Nitrogen Dioxide.
Ozone is made up of three oxygen atoms and is formed when sunlight and heat lead to chemical reactions between nitrogen dioxide and a volatile organic compound also known as hydrocarbons. This reaction can occur high in the atmosphere and low to the ground. As a result of the increasing amount of UV radiation emitted during the long days of summer, higher ground-level ozone occurs often. It is worthy to note that ozone is good up high and bad near the ground.