Which gas is primarily responsible for ozone layer depletion?

Chlorofluorocarbons (CFCs) are primarily responsible for ozone layer depletion due to their unique chemical properties and behavior in the atmosphere. When CFCs are released into the atmosphere, they eventually rise to the stratosphere, where they are subjected to ultraviolet (UV) radiation. This radiation breaks down CFC molecules, releasing chlorine atoms.

The released chlorine is highly reactive and can destroy ozone (O3) molecules in a catalytic cycle. For each chlorine atom, it is capable of breaking apart thousands of ozone molecules before it is eventually removed from the atmosphere. This process leads to a significant thinning of the ozone layer, which is crucial for protecting living organisms on Earth from harmful UV radiation.

In contrast, carbon dioxide, nitrous oxide, and methane do not have the same destructive effect on ozone molecules. While they are greenhouse gases and contribute to climate change, they do not participate in the chemical reactions that lead to ozone depletion. Therefore, CFCs are the primary agents of ozone layer depletion, making this answer correct.