Answer:
The correct answer would be A] Ethyl alcohol.
Yeast undergo fermentation in absence of oxygen.
In anaerobic conditions, yeast converts one molecule of glucose into two molecules of ethanol and two molecules of carbon dioxide.
Glycolysis is common in both aerobic and anaerobic respiration. So, first glucose is converted into 2 molecules of pyruvate with net gain of 2 ATP (adenosine triphosphate) and 2 NADH.
Pyruvate is then converted into alcohol (ethanol) in a two-step manner.
First, it is converted into acetaldehyde which is catalyzed by pyruvate decarboxylase. One molecule of CO₂ is released as a byproduct.
Acetaldehyde is then converted into ethanol with the help of alcohol dehydrogenase. It regenerates NAD⁺ lost in glycolysis. It ensures that the cell can continuously use glycolysis as the source of ATP.