The carbon cycle involves an exchange of carbon between
a. the geosphere and atmosphere
b. the atmosphere and hydrosphere
c. the geosphere and hydrosphere
d. the geosphere, hydrosphere, and atmosphere

D) The geosphere, hydrosphere, and atmosphere

During the carbon cycle, various processes move carbon from the geosphere to the atmosphere such as volcanic eruptions release carbon dioxide from molten rock beneath the earth's surface to the atmosphere. Carbon can leave the soil through soil respiration which releases CO2, or by erosion  which can carry it into rivers or the ocean, where it then enters the hydrosphere. Carbon is found in the hydrosphere dissolved in ocean water and lakes and hence the cycle continues.

The carbon cycle is the biogeochemical cycle which involves an exchange of carbon among the biosphere, pedosphere, geosphere, hydrosphere, and atmosphere of the Earth.

Carbon is the most important component of the biological compounds  such as limestone. Also, during soil respiration, Carbon can leave the soil through it which releases ,  which carries it into the rivers or the ocean, where it then enters the hydrosphere.

Thus, option D is correct.