Answer is: A. spontaneous reactions release.
ATP is short for adenosine triphosphate
Adenosine triphosphate converts to either the adenosine diphosphate (ADP) or adenosine monophosphate (AMP), in this process energy is released (for example glycolysis, the citric acid cycle or oxidative phosphorylation and beta-oxidation). ATP is made of three components: the triphosphate, the sugar ribose and a nitrogenous base (adenine).