Final answer:
The d. lithosphere is not considered one of the three major reservoirs of the global carbon cycle; instead, the major reservoirs are the atmosphere, oceans, and terrestrial ecosystems.
Step-by-step explanation:
The area that is not one of the three major reservoirs of the global carbon cycle is D) Lithosphere. The major reservoirs of carbon in the carbon cycle are the atmosphere, oceans, and terrestrial ecosystems.
Although the lithosphere contains carbon in the form of fossil fuels and sedimentary rock structures like limestone, it is not considered one of the principal active reservoirs in the ongoing exchange of carbon, because the exchange occurs over much longer geologic timescales.
The biogeochemical carbon cycle involves the movement of carbon through land, water, and air. The atmosphere is a major reservoir of carbon, primarily in the form of carbon dioxide. This carbon dioxide is essential for the process of photosynthesis and exchanges constantly with carbon in the ocean, which contains the largest carbon reservoir in the form of calcium carbonate in marine sediments.