The total NADH formed by one glucose molecule during the Krebs cycle is

Explanation

The total NADH formed by one glucose molecule during the Krebs cycle is 6. Each glucose is converted into two acetyl-CoA molecules, and each acetyl-CoA produces 3 NADH in one turn of the cycle, giving a total of 6 NADH per glucose. The 3 NADH option is incorrect because it accounts for only one acetyl-CoA, not both. The 8 NADH option is too high and does not match the actual NADH generated in the Krebs cycle, though the total NADH, including glycolysis and the link reaction, may be higher. The option of 4 NADH underestimates the amount, as two acetyl-CoA molecules produce 6 NADH in total.