Which of the following protects the Earth from high-energy ultraviolet (UV) light?

• A. The greenhouse effect
• B. The nitrogen cycle
• C. The carbon cycle
• D. The ozone layer

Answer: (D)

Verified step by step guidance

1. Understand the role of ultraviolet (UV) light: UV light is a type of electromagnetic radiation emitted by the sun. High-energy UV light can be harmful to living organisms, causing damage to DNA and increasing the risk of skin cancer.
2. Learn about the ozone layer: The ozone layer is a region of Earth's stratosphere that contains a high concentration of ozone (O₃) molecules. It plays a critical role in absorbing and blocking most of the sun's harmful UV radiation.
3. Differentiate the options provided: The greenhouse effect refers to the trapping of heat by greenhouse gases, which helps regulate Earth's temperature but does not block UV light. The nitrogen cycle and carbon cycle are processes that involve the movement of nitrogen and carbon through ecosystems, but they are unrelated to UV protection.
4. Recognize the correct answer: The ozone layer is specifically responsible for protecting Earth from high-energy UV light by absorbing it before it reaches the surface.
5. Conclude the importance of the ozone layer: Without the ozone layer, life on Earth would be exposed to harmful levels of UV radiation, highlighting its essential role in maintaining a habitable environment.