The correct answer is option 2: Chlorofluorocarbon (CFC). CFCs are synthetic compounds primarily used in refrigeration, air conditioning, and aerosol propellants. These compounds have been identified as one of the main contributors to the depletion of the ozone layer. When released into the atmosphere, CFCs rise and reach the ozone layer. The chlorine atoms present in CFCs can then catalytically destroy ozone molecules. This leads to the thinning of the ozone layer, which is essential for protecting life on Earth from harmful ultraviolet (UV) radiation. Carbon dioxide (option 1), nitrogen oxide (option 3), and sulfur dioxide (option 4) are not directly responsible for ozone layer depletion. Carbon dioxide is a greenhouse gas that contributes to climate change. Nitrogen oxide and sulfur dioxide are mainly associated with air pollution and acid rain.