The correct option is Ultraviolet radiation.
Explanation
The Earth's atmosphere is stratified into layers based on temperature profiles. The stratosphere, extending from approximately 10 to 50 kilometers above the Earth's surface, contains the ozone layer. This layer is characterized by a high concentration of ozone ($O_3$) molecules.
Detailed Analysis:
- Ultraviolet radiation is Correct: The primary function of the stratospheric ozone layer is to absorb the majority of the Sun's harmful Ultraviolet (UV) radiation, specifically UV-B (280-315 nm) and UV-C (100-280 nm). By filtering out this high-energy radiation, the ozone layer prevents severe biological damage, such as skin cancer, cataracts, and DNA mutation in living organisms.
- Infrared radiation is Incorrect: Infrared (IR) radiation is associated with thermal energy. While ozone acts as a greenhouse gas and can absorb outgoing terrestrial infrared radiation, its defining and most critical role in the stratosphere is the absorption of incoming solar UV radiation.
- Visible light is Incorrect: Visible light passes through the atmosphere to reach the surface, enabling vision and photosynthesis. It is not the primary target of absorption by the ozone layer.
- Radio waves is Incorrect: Radio waves are long-wavelength electromagnetic waves. They are typically reflected by the ionosphere (part of the thermosphere), which facilitates long-distance communication, but they are not absorbed by the ozone layer.
Key Takeaway: The stratospheric ozone layer acts as a vital shield for the biosphere by absorbing harmful Ultraviolet (UV) radiation from the Sun.