Correct Answer: Ozone-depleting substances

Solution : The correct answer is (d) Ozone-depleting substances

The Montreal Protocol is an international environmental agreement that was implemented in 1989. Its primary goal is to protect the Earth's ozone layer by phasing out the production and consumption of substances that are known to deplete ozone in the stratosphere.

These ozone-depleting substances (ODS) include chlorofluorocarbons (CFCs), hydrochlorofluorocarbons (HCFCs), halons, carbon tetrachloride, and methyl chloroform. These substances were commonly used in various industrial and consumer applications, such as refrigeration and air conditioning, aerosols, foam-blowing agents, and fire extinguishers.

The production and use of ODS can release chlorine and bromine atoms into the atmosphere, which then catalytically destroy ozone molecules in the stratosphere. This leads to the thinning of the ozone layer, particularly in the polar regions, resulting in the formation of the ozone hole.

The Montreal Protocol has been successful in phasing out the use of ODS through international cooperation and regulation. It has led to a significant reduction in the emissions of ODS, contributing to the recovery and protection of the ozone layer.