Which part of cellular respiration must occur before any of the other steps can occur A. Pyruvate processing B. Electron transport chain C. Glycolysis D. Krebs cycle?

C. Glycolysis must occur before any of the other steps in cellular respiration. It is the first stage of the process, where glucose is broken down into pyruvate, producing a small amount of ATP and NADH. The pyruvate produced then enters either pyruvate processing or the Krebs cycle, depending on the presence of oxygen.