• Anaerobic Glycolysis: In tissues lacking oxygen or lacking mitochondria (such as mature mammalian red blood cells), pyruvate cannot undergo oxidative decarboxylation into acetyl-CoA.
• End Product: Pyruvate is reduced to lactate by cytosolic lactate dehydrogenase (LDH):

• Significance: This reaction is essential because it re-oxidizes $\text{NADH}$ to $\text{NAD}^+$, which is required by glyceraldehyde-3-phosphate dehydrogenase (GAPDH) to maintain ongoing ATP generation via substrate-level phosphorylation.

Correct option: (3) Lactate