D)
The process described in the picture is oxidative decarboxylation, which is followed by Krebs cycle.
The first stage in cell respiration is Glycolysis, which produces Pyruvate, ATP and NADPH. Then Pyruvate can go through Fermentation, which does not produce any more energy, or go through oxidative decarboxylation, which prepairs it for Krebs cycle. If pyruvate is decarboxylated, then it goes through Krebs cycle, producing GTP and more NADH. Then all NADHs would go into Electron transport chane, producing a lot more ATP.
