Which term describes the process by which carbon cycles through organisms and the environment?

• A. Limiting factor
• B. Organ system
• C. Carbon cycle
• D. Producer

Answer: (C)

Carbon cycle describes how carbon moves through air, water, soil, rocks, and living things. It involves carbon being taken up by plants during photosynthesis, stored in organic matter, and then released back into the environment through respiration, decay, and decomposition. Human activities like burning fossil fuels also release carbon back into the atmosphere. The ocean exchanges carbon with the atmosphere as CO2 dissolves and is taken up by marine organisms, while weathering of rocks slowly adds carbon to soils and oceans. This continuous movement keeps carbon available for life and helps regulate the climate.

The other terms don’t fit the idea of a moving system for carbon. A limiting factor is something that restricts growth or a process's rate, not the pathway carbon follows. An organ system is a group of organs in an organism, not the carbon movement itself. A producer is an organism that makes its own organic matter, which is part of the cycle but not the term for the process describing carbon’s movement.