Ozone protects biosphere from

The correct answer is B) Ultraviolet rays. The ozone layer sits in the stratosphere, roughly 15 to 35 km up, and absorbs most of the harmful UV radiation from the Sun. It takes in almost all UV-C and most of the UV-B, which would otherwise damage DNA, cause skin cancer and cataracts, and harm phytoplankton and crops.

• A) Infra-red rays: Ozone is not the shield against infrared. Infrared is trapped by greenhouse gases such as water vapour, CO2 and methane, and ozone plays only a minor role in that.
• C) X-rays and D) Gamma rays: These high-energy rays are absorbed far higher up, in the thermosphere and ionosphere, by atoms and molecules like nitrogen and oxygen. Ozone is not the agent here.

The core concept is stratospheric ozone as a UV filter, and it links to the Montreal Protocol (1987), which phased out CFCs that were depleting the ozone layer. The ozone layer is now recovering, and that recovery is a standard Environment and Mains topic.

Trap: Candidates mix up ozone's role as a UV absorber with its minor greenhouse role, or assume that because ozone is in the atmosphere it blocks all high-energy rays.