Which letter in the diagram corresponds to a substance that is formed from the photolysis of nitrogen dioxide but can also result from stratospheric penetrations?

Photolysis

The decomposition or separation of molecules by the action of light.

Stratospheric Penetrations

The entry or movement of substances or objects into the stratosphere, the second major layer of Earth's atmosphere.

Nitrogen Dioxide

A toxic, reddish-brown gas (NO2) that is a significant air pollutant, resulting from the combustion of fossil fuels and is associated with respiratory diseases.