The main way of ATP production in the body is
Correct answer: A. oxidative phosphorylation
Oxidative phosphorylation is the primary method of ATP production in most cells. Substrate-level phosphorylation occurs directly within metabolic pathways, while the citric acid cycle generates intermediates used for energy but not ATP directly. Phosphocreatine breakdown provides a rapid source of phosphate groups but is not the main way of ATP production.