Answer: The correct answer would be lactic acid fermentation.
Step-by-step explanation:
In humans, specially in muscle cells, lactic acid fermentation takes place during high intensity exercise. During exercise when oxygen supply fails to meet the demands of muscle, they undergo lactic acid fermentation instead of cellular respiration.
During this process, the pyruvate (end product of glycolysis) is converted into the lactate with the help of enzyme lactate dehydrogenase.
It regenerates NAD⁺ lost in the glycolysis and thus, helps in continuous working of glycolysis.