In an environment without oxygen, which alternative pathway restores the oxidized carrier needed by glycolysis?

1. If oxygen is available, NADH is oxidized readily, though indirectly, through the electron transport chain. 2. Without oxygen that route is closed, so another way of oxidizing NADH is needed. 3. Fermentation is the alternate pathway that provides that oxidation. 4. Chemiosmosis is the oxygen-dependent route itself, so it cannot be the anaerobic answer. _Source: OpenStax Biology (1st ed., CC BY 4.0), Ch 7 "Cellular Respiration", section 7.2 Glycolysis_