Distinguish between the carbon cycle and the water cycle in environmental chemistry.

• A. The carbon cycle tracks carbon in oceans only.
• B. The carbon cycle tracks carbon in rocks.
• C. The carbon cycle involves only living organisms; the water cycle is only rainfall.
• D. The carbon cycle tracks carbon among air, water, land, and organisms; the water cycle tracks the movement of water through evaporation, condensation, precipitation, and runoff.

Answer: (D)

The key idea is that cycles describe how a substance moves through different parts of the environment via specific processes. For carbon, it’s about how carbon moves among air, water, land, and living organisms, with exchanges with oceans, soils, and rocks and processes like photosynthesis, respiration, decay, and geological storage. The water cycle, on the other hand, follows the movement of water itself through evaporation, condensation, precipitation, infiltration, runoff, and storage in bodies of water and groundwater. The best choice captures these distinct pathways: carbon cycles through air, water, land, and organisms, while water moves through evaporation, condensation, precipitation, and runoff. The other statements miss important aspects: carbon isn’t limited to oceans or rocks, and the water cycle isn’t just rainfall but a continuous movement of water through phase changes and landscapes.