What is the major function of ozone in the stratosphere?

• A. To regulate weather patterns
• B. To trap heat near Earth's surface
• C. To react with nitrogen oxides to form smog
• D. To absorb and reflect UV rays from the sun

Answer: (D)

Ozone in the stratosphere mainly serves as a shield against ultraviolet radiation from the sun. By absorbing most of the sun’s UV-B and UV-C rays, it prevents a large portion of harmful radiation from reaching Earth's surface, protecting living organisms from DNA damage, skin cancer, and ecological harm. The idea here is absorption—the ozone layer blocks and reduces UV exposure rather than primarily reflecting it. The other options don't fit because weather patterns are controlled by atmospheric dynamics, not the ozone layer; trapping heat near the surface is the role of greenhouse gases in the lower atmosphere; and smog formation occurs in polluted air at the ground level, not from stratospheric ozone.