Answer:
A. oxygen-energy system
Explanation:
Aerobic cellular respiration, that is, oxygen energy system includes oxidation of nutrients in presence of oxygen. Glucose is broken down into pyruvate by glycolysis which in turn enters the Kreb's cycle in form of acetyl CoA. Fats are broken down into acetyl CoA by beta oxidation and enter the Kreb's cycle. Acetyl CoA is converted into CO2 and H2O and the released energy is stored in form of NADH and FADH2 which then enter the oxidative phosphorylation and drive the ATP synthesis. Hence, oxygen energy system retrieves the energy from fats and glucose and store it in form of ATP.
