What process primarily contributes to the depletion of the ozone layer?

The depletion of the ozone layer is primarily caused by the emissions of chlorofluorocarbons (CFCs), which are chemicals that were widely used in refrigeration, air conditioning, aerosol sprays, and foam-blowing applications. When CFCs are released into the atmosphere, they eventually rise up to the stratosphere, where ultraviolet (UV) radiation from the sun breaks them down. This process releases chlorine atoms, which can destroy ozone (O3) molecules, leading to a thinning of the ozone layer.

The ozone layer is crucial because it absorbs the majority of the sun's harmful UV radiation; its depletion not only affects the environment but also has serious implications for human health, including increased risks of skin cancer and cataracts.

In this context, while other processes like industrial pollution indirectly contribute to environmental issues, and photosynthesis and respiration are essential biological processes, they do not significantly impact the ozone layer's health like CFC emissions do. This highlights the specific and detrimental role of CFCs in ozone depletion compared to the other choices provided.