Final answer:
The true statement about the carbon cycle in nature is that carbon sinks include forests and oceans, which absorb more carbon than they emit through processes like photosynthesis.
Step-by-step explanation:
The correct answer to the question of which statement is true of carbon as it cycles in nature is option C, Carbon sinks include forests and oceans. Carbon sinks refer to systems that absorb more carbon than they emit, and forests, as well as oceans, play significant roles in this process. Through photosynthesis, forests absorb carbon dioxide and store it in the form of biomass. Similarly, oceans absorb a large amount of carbon dioxide from the atmosphere, both directly through the water’s surface and indirectly by the life forms residing within them that also engage in photosynthesis.
Photosynthesis removes carbon dioxide from the atmosphere and utilizes it to create organic compounds. Conversely, living organisms release carbon dioxide during cellular respiration. Additional carbon dioxide release occurs when organisms die and decompose, and when carbon-rich materials like fossil fuels are burned.
Geological activities, such as volcanic eruptions and the heating of limestone to produce cement, also release stored carbon dioxide back into the atmosphere. Oceanic processes contribute to the carbon cycle by absorbing and releasing carbon dioxide depending on water temperature changes.