The NADH that enters the Electron Transport System is produced by all of the following processes except:

glycolysis

transition reaction

fermentation

Krebs cycle

The correct answer is option C

In glycolysis 2 molecules of NADH are produced per glucose molecule, In transition reaction 1 molecule of NADH per pyruvate is produced and in Krebs cycle 3 NADH molecules per acetyl-CoA are produced. In Fermentation - NADH is produced but not for an electron transport chain.