Which of the following elements is released into the atmosphere by all of these processes: volcanic outgassing, animal respiration and flatulence, burning of fossil fuels, and metamorphism of limestone?
a. carbon.
b. nitrogen.
c. oxygen.
d. sulfur

a. Carbon

Explanation:

During volcanic outgassing is a process whereby volcanic eruptions emits gases to the atmosphere. Examples of gases released are carbon dioxide and water vapor. The respiration of animal takes in oxygen and gives out carbon dioxide. Flatulence is the release of gas (i.e. carbon dioxide) from the digestive system out of the back passage. The burning of fossil fuel also releases carbon dioxide. Metamorphism of limestone is when limestone is subjected to pressure and heat. Carbon is the element that is present in all these processes.

4d^55s^1 ( third choice)