The Montreal Protocol is aimed at phasing out ozone-depleting substances.

• A. Phasing out ozone-depleting substances
• B. Addressing water pollution
• C. Reducing greenhouse gas emissions only
• D. Promoting recycling

Answer: (A)

Protecting the ozone layer by phasing out ozone-depleting substances is what the Montreal Protocol is all about. ODS like chlorofluorocarbons and halons were found to break down ozone in the stratosphere, allowing more ultraviolet radiation to reach the Earth's surface. The protocol, adopted in 1987, pushes countries to stop using these substances and to switch to safer alternatives, with schedules and amendments to tighten controls over time. That makes this option the best fit—the treaty is specifically about eliminating substances that harm the ozone layer, not about water pollution, simply reducing greenhouse gas emissions, or promoting recycling in general. While some ozone-depleting substances are also greenhouse gases, the main aim is the phase-out of ODS to protect the ozone layer.