Which statement correctly describes stratospheric ozone?

• A. It blocks most ultraviolet radiation from entering the troposphere
• B. It traps heat in the lower atmosphere
• C. It is the primary component of atmospheric oxygen
• D. It is a major source of rainfall

Answer: (A)

The statement centers on how the ozone layer in the stratosphere acts as a shield against the sun’s ultraviolet radiation. Ozone (O3) in that layer absorbs most of the sun’s high-energy UV photons, especially UV-B and UV-C, so far less of that harmful radiation reaches the troposphere and the surface. This shielding is why life on Earth isn’t constantly exposed to intense UV damage and why protecting the ozone layer matters.

The other options don’t fit because:

• Stratospheric ozone’s key role isn’t to trap heat in the lower atmosphere; while ozone absorption does warm the stratosphere, its primary relevance here is UV shielding, not a greenhouse effect on the lower layers.

• It is not the main component of atmospheric oxygen—oxygen in the air is primarily O2, with ozone being a much smaller, reactive component.

• It isn’t a major source of rainfall; rainfall is driven by hydrological and climatic processes, not ozone chemistry.

So the correct idea is that stratospheric ozone blocks most ultraviolet radiation from entering the lower atmosphere, protecting living organisms from UV harm.