Which of the following has the highest Ozone Depletion Potential?

The answer is D-CFCs because Chlorofluorocarbons (CFCs) have historically been recognized as substances with a high Ozone Depletion Potential (ODP). CFCs release chlorine atoms when they are broken down in the stratosphere, and a single chlorine atom can destroy thousands of ozone molecules. This significant impact on the ozone layer is why CFCs were targeted and phased out under the Montreal Protocol.

In contrast, A-HFOs (Hydrofluoroolefins), B-HCFCs (Hydrochlorofluorocarbons), and C-HFCs (Hydrofluorocarbons) generally have much lower Ozone Depletion Potentials. HCFCs are considered transitional substances with lower potency than CFCs, and HFCs do not deplete the ozone layer at all but are still potent greenhouse gases. A-HFOs represent an even more environmentally friendly option with a minimal ODP, focusing on reducing the environmental impact associated with traditional refrigerants.

Since CFCs are the most harmful to the ozone layer among the options, they are identified as having the highest Ozone Depletion Potential.