What does the term 'carbon cycle' refer to?

The term 'carbon cycle' refers to the continuous transfer of carbon through Earth's systems. This cycle encompasses a series of processes in which carbon is exchanged among the atmosphere, land, ocean, and living organisms. Carbon exists in various forms, such as carbon dioxide in the atmosphere, organic matter in living organisms, and carbonates in rocks and oceans.

Throughout the carbon cycle, processes like photosynthesis, respiration, decomposition, and combustion play crucial roles in moving carbon between these different reservoirs. For example, plants absorb carbon dioxide during photosynthesis, converting it into organic compounds, while animals release carbon dioxide back into the atmosphere through respiration. This dynamic movement of carbon is vital for maintaining the balance of ecosystems and regulating Earth's climate.

The other choices pertain to specific aspects of carbon management or impact but do not capture the essence of the carbon cycle itself. Carbon trading refers to markets designed to incentivize reductions in greenhouse gas emissions, the accumulation of carbon in the atmosphere is one outcome of increased emissions without corresponding absorption, and the reduction of carbon emissions globally is a goal related to climate change efforts but does not describe the cycle of carbon as it naturally occurs on Earth.