Final answer:
The three reservoirs of the carbon cycle are rocks, oceans, and the atmosphere, which all play significant roles in storing and cycling carbon through the environment.
Step-by-step explanation:
The three main reservoirs of the carbon cycle are rocks, oceans, and the atmosphere. The atmosphere acts as a major carbon reservoir, primarily in the form of carbon dioxide (CO2), which plays a critical role in photosynthesis. Oceans store carbon in various ways, including dissolving atmospheric CO2 and housing marine organisms whose shells contribute to sedimentary deposits over time. Rocks, particularly sedimentary rocks such as limestone, also represent a significant carbon store, as they are formed from the compressed remains of marine organisms that incorporate carbon into their shells.