The formation of ozone hole in the Antarctic region has been a cause of concern. What could be the reason for the formation of this hole?

The correct answer is B. The Antarctic ozone hole forms in the lower stratosphere during the cold southern winter and spring. Under these extremely low temperatures, a strong polar front and circumpolar vortex isolate the polar air mass, and polar stratospheric clouds form on their ice-like particles. Chlorofluorocarbons (CFCs) rising from the troposphere are converted there into reactive chlorine, which is released on cloud surfaces and destroys ozone catalytically once sunlight returns in spring.

• A is wrong: tropospheric turbulence plays no role here, and the ozone hole is a stratospheric phenomenon.
• C is wrong: the polar front and stratospheric clouds are essential to the chemistry, not absent. Methane is not the key ozone-depleting agent in this context.
• D is wrong: the hole is linked to extreme cold, and warming would reduce cloud formation rather than cause the hole.

The core concept is heterogeneous chemistry on polar stratospheric clouds, which connects to the Montreal Protocol (1987) and India's commitments under it. This is a standard Environment and Science and Technology topic with Mains relevance on global commons and international treaties. The ozone layer is now showing signs of recovery after the phase-out of CFCs, so describe the situation in the past or present tense with care.

Trap: Aspirants pick A or D because they associate ozone loss with 'turbulence' or 'global warming', forgetting that the cold stratosphere and CFC-driven chlorine chemistry is the core mechanism.