Which statement best describes the environmental role of chlorofluorocarbons (CFCs)?

• A. CFCs are greenhouse gases primarily from refrigerants and do not affect the ozone layer.
• B. CFCs are harmless and occur naturally.
• C. CFCs are greenhouse gases primarily from refrigerants and contribute to ozone depletion.
• D. CFCs are primarily emitted by volcanic activity.

Answer: (C)

Chlorofluorocarbons are long‑lived, human‑made chemicals released mainly from refrigerants, foam-blowing agents, and certain solvents. They trap heat in the atmosphere as greenhouse gases, contributing to global warming. At the same time, when they reach the stratosphere, ultraviolet light breaks them apart and releases chlorine atoms that catalytically destroy ozone, thinning the ozone layer. This dual role—being greenhouse gases and depleting the ozone layer—explains why the statement that CFCs are greenhouse gases primarily from refrigerants and contribute to ozone depletion is the best description. They are not harmless or natural substances, and their main sources are not volcanic activity.