Explanation: The electron transport chain generates the most ATP out of all three major phases of cellular respiration. Glycolysis produces a net of 2 ATP per molecule of glucose.
The Krebs cycle takes place inside the mitochondria. The Krebs cycle produces the CO2 that you breath out. This stage produces most of the energy ( 34 ATP molecules, compared to only 2 ATP for glycolysis and 2 ATP for Krebs cycle).