Which of the following statements is most accurate? A. A finite amount of carbon exists on Earth, and it moves through living and nonliving materials through the carbon cycle.
B. The amount of carbon on Earth cycles, gradually increasing as it moves up the food chain, and decreasing until the next phase of the cycle.
C. Carbon flows through the food chain as animals eat it, then decomposes and is permanently removed from the system when the food chain is complete.
D. Carbon enters Earth's atmosphere when animals exhale, then moves into space where its amount steadily increases, and finally moves back into Earth's atmosphere to be used again.