Depletion of the ozone layer is caused due to

The correct option is Freons.

Step-by-step Explanation:
1. What are Freons?
Freons are a group of chlorofluorocarbons (CFCs) containing carbon, chlorine, and fluorine atoms. They are highly stable, non-toxic, non-corrosive, and non-inflammable synthetic organic compounds widely used as refrigerants, propellants in aerosol sprays, and solvents.

2. Atmospheric Transport:
Once released into the atmosphere, Freons are extremely unreactive in the lower atmosphere (troposphere) and gradually diffuse intact into the upper atmosphere (stratosphere) over several years.

3. Photodissociation by UV Radiation:
In the stratosphere, Freons are exposed to powerful solar ultraviolet (UV) radiation. This high-energy light breaks the carbon-chlorine bonds, releasing highly reactive chlorine free radicals (represented as Cl^•):

$${\mathrm{CF}}_2{\mathrm{Cl}}_2\stackrel{\mathrm{UV}}{\to }{\mathrm{CF}}^2{\mathrm{Cl}}^{•}+{\mathrm{Cl}}^{•}$$

4. Catalytic Destruction of Ozone:
The chlorine radical reacts with ozone ($O_3$) molecules in a catalytic cycle, converting ozone into molecular oxygen ($O_2$) and forming chlorine monoxide radicals (ClO^•):

$${\mathrm{Cl}}^{•}+O_3\to {\mathrm{ClO}}^{•}+O_2$$

The chlorine monoxide radical then reacts with atomic oxygen in the stratosphere, regenerating the chlorine radical:

$${\mathrm{ClO}}^{•}+O\to {\mathrm{Cl}}^{•}+O_2$$

5. Conclusion:
Because the chlorine radical is regenerated in this process, a single molecule of Freon can destroy thousands of ozone molecules. This continuous depletion reduces the concentration of the stratospheric ozone layer, which shields Earth from harmful UV radiation. Therefore, Freons are the primary cause of ozone layer depletion among the options listed.