Final answer:
ATP is not made by substrate-level phosphorylation during fermentation. Fermentation regenerates NAD+ to allow glycolysis to continue but does not directly generate more ATP beyond what glycolysis provides.
Correct option is c) Electron transport chain
Step-by-step explanation:
During fermentation, ATP is not made by substrate-level phosphorylation. Glycolysis, the Krebs cycle, and the electron transport chain all involve processes that can generate ATP via different mechanisms. Glycolysis and the Krebs cycle both produce ATP by substrate-level phosphorylation. However, the electron transport chain produces ATP through a process known as oxidative phosphorylation, which involves the transfer of electrons through a chain of proteins in the cell's membrane and uses a chemiosmotic gradient to produce ATP.
Fermentation is a process that allows cells to continue producing ATP via glycolysis when oxygen is scarce by regenerating the electron carrier NAD+ from NADH. Although glycolysis itself produces a small amount of ATP, during fermentation, there is no additional ATP produced directly by this pathway, unlike the Krebs cycle and the electron transport chain that follows.