Answer: d. Niacin
Step-by-step explanation:
Many vitamins are parts of coenzymes. In numerous oxidation-reduction reactions that are catalyzed by enzymes, the electrons pass in pairs from the active site of the enzyme to a coenzyme that serves as the electron acceptor. Vitamin B3 or Niacin is used to construct the coenzymes NADH and NADPH, their sources for human ingestion are liver, lean meats, and grains. Its deficiency in consumption leads to Pellagra, inflammation of nerves and mental disorders.