Answer:
The correct answer is - reduction by accepting an electron from NADH.
Step-by-step explanation:
During fermentation, the conversion of the pyruvate into lactic acid takes place which is a part of the anaerobic process. This process required a reducing agent to accept the electron by pyruvate and convert it to lactic acid.
Pyruvate + NADH → Lactic acid + NAD+
NADH oxidized again for the glycolysis process in anaerobic conditions.