What would earth’s atmosphere likely consist mostly of without the presence of life?
a. oxygen
b. nitrogen
c. water vapor
d. carbon dioxide

B. nitrogen. because of the fact that there would be no plants to produce oxygen as a waste product and there would not be much carbon dioxide because animals are not dying, they do not even exist and there would be water vapor but there would mostly be nitrogen. 

Processes above and be sure to mention the movement of electrons and energy as the carbon atom moves from one reaction to another.