The depletion of the ozone layer is mainly caused by halogen ( Cl,Br ) and nitrogen oxides ( NOx ) that catalytically destroy ozone (O3) molecules in the stratosphere. The main culprits are: CFCs (chlorofluorocarbons) such as CF2Cl2 (Freon-12). NO and NO2 (from supersonic aircrafts, etc.) to a limited extent. - Option A: NO Nitric oxide (NO) can indeed react with ozone and participate in catalytic cycles that destroy ozone. So NO does contribute to ozone layer depletion. ✔ Primarily responsible. - Option B: CF2Cl2 (CFC-12) A chlorofluorocarbon that releases chlorine radicals ( Cl ) under UV light in the stratosphere. These radicals catalytically destroy ozone. CFCs are the principal cause of ozone layer depletion. ✔ Primarily responsible. - Option C: CH4 (Methane) Methane does not destroy ozone directly. In fact, methane can react with Cl⋅ radicals, forming HCl and thereby reducing the concentration of ozone-depleting radicals to some extent. It is not a major ozone-depleting substance. - Not primarily responsible. - Option D: Cl2 (Chlorine gas) Though molecular chlorine can destroy ozone, it doesn't reach the stratosphere in large amounts due to high reactivity and solubility. However, under certain conditions, Cl2 produced from CFC photolysis can release Cl atoms - so it is indirectly involved. - Can contribute, though not directly emitted into stratosphere. Final Answer: CH4 Methane ( CH4 ) is not primarily responsible for depletion of the ozone layer in the stratosphere.
