Part 1: The process which arrow C represent is the burning of fossil fuels to introduce Carbon Dioxide (CO₂) into the atmosphere. This process in the Carbon Cycle is relatively new since humans weren't able to produce large amounts of Carbon Dioxide by burning fossil fuels until the Industrial Revolution. This could also represent the process of cement manufacturing since it releases CO₂ by the following reaction:
CaCO₃ → CaO + CO₂
Part 2: A process that could release the compound into the air is the burning of fuels. This is an oxidation reaction in which the carbon present in form of Hydrocarbons in the fuel is oxidized to CO₂ by the oxygen in the atmosphere. The CO₂ produced is in the gaseous state, and is incorporated into the air. It also contributes to the greenhouse effect. The combustion reaction for the most simple hydrocarbon, methane (CH₄) is shown below:
CH₄ (g) + 2O₂(g) → CO₂(g) + 2H₂O (g)
Part 3: The elements that form it are conserved during carbon cycle by the Law of Conservation of Matter. This Law states that in chemical reactions, the matter is neither produced nor consumed, it only transforms. So, during all chemical processes in the Carbon Cycle, Carbon atoms are never destroyed but they change and rearrange into different molecules. This cycle is key to the sustaining of life on Earth.