How did the carbon atom get from land animals back to the atmosphere?

How did the carbon atom get from land animals back to the atmosphere? The animal releases the carbon back into the air by the process of cellular respiration.

The atmosphere is the air above Earth's surface. The hydrosphere is composed of all of Earth's water.

the cell cycle is the final answer! : )

hydrogen is a compound or a single element and a element is a pure substence that cannot be separated into simpler subtances

clorine is a compound its a chemical substance that forms when two or more different elements combine

so both hydrogen and clorine are compounds