Answer:
The correct answer is "flux".
Step-by-step explanation:
The four main carbon reservoirs on Earth are located in the atmosphere, the terrestrial biosphere, the oceans and the sediments. Any movement of carbon between carbon reservoirs is called a flux. It is possible to estimate the net direction and magnitude of the carbon fluxes, however there are several processes that are responsible for these fluxes, including: photosynthesis, respiration, decomposition, combustion, among others.