Ozone hole refers to:

Correct option is C

The term "ozone hole" refers to a significant reduction in the concentration of ozone in the stratosphere, particularly over the polar regions. This phenomenon is primarily observed over Antarctica during the Southern Hemisphere’s spring (September to November). It is caused mainly by human-made chemicals like chlorofluorocarbons (CFCs), which release chlorine and bromine atoms that destroy ozone molecules.
Important Points:
The ozone layer is located in the stratosphere, a region of the Earth's atmosphere about 10-30 km above the surface.
The ozone layer protects life on Earth by absorbing most of the Sun's harmful ultraviolet (UV) radiation.
The depletion of ozone allows more UV-B radiation to reach the Earth’s surface, increasing the risk of skin cancer, cataracts, and other environmental impacts.
Chlorine and bromine compounds are the primary culprits behind ozone depletion. They break down ozone molecules (O₃) into oxygen molecules (O₂).
The Montreal Protocol, an international treaty, was established in 1987 to phase out the use of ozone-depleting substances (ODS), and it has helped reduce the size of the ozone hole.
Information Booster:
• The ozone hole is not a literal hole but rather a region of thinned ozone.
• The ozone depletion is most severe over Antarctica due to the unique weather conditions, particularly the polar stratospheric clouds.
• The Montreal Protocol has been successful, and the ozone layer is showing signs of recovery, but it may take decades to return to pre-1980 levels.
• UV-B radiation increases due to the thinning of the ozone layer, leading to higher risks of skin cancer and eye damage.
• The impact of ozone depletion extends beyond human health; it also affects marine ecosystems and terrestrial plant life.
• Global cooperation and adherence to international treaties are critical to maintaining the recovery of the ozone layer.
Additional Knowledge:
(a) Increase in density in ozone layer: This is incorrect, as the term "ozone hole" does not refer to an increase in ozone density but rather a reduction in its concentration.
(b) None of these: Incorrect because option (c) accurately describes the phenomenon of the ozone hole.
(d) Increase in the ozone layer in troposphere: This is incorrect. An increase in ozone in the troposphere is related to ground-level ozone, a harmful pollutant, and not the depletion observed in the stratosphere.