If glucose is metabolized under completely anaerobic conditions, pyruvate ( Please explain why each answer is wrong or right.) a. immediately enters the Krebs cycle.
b. is converted by fermentation to lactate or CO2 and ethanol.
c. is converted back to fructose until the concentration of oxygen increases.
d. is converted to NADH.

B.

Explanation:

A is wrong because pyruvate would enter the Krebs cycle under aerobic condition (when oxygen is present). Hence the name aerobic cellular respiration

C. I do not really too much about fructose or the concentration of oxygen, but I can assure that this answer choice is not correct.

D is wrong because NADH would be converted from NADP+. Either with oxidation or reduction, and this helps to keep this process going.

B is correct because fermentation is another word for anaerobic cellular respiration. The process takes place with the absence of oxygen. It either goes through Alcoholic or lactic acid fermentation.

I hope this helps!