What is produced alongside ethanol during alcoholic fermentation?

During alcoholic fermentation, which is primarily carried out by yeast, glucose is converted into ethanol and carbon dioxide. The process is anaerobic, meaning it occurs in the absence of oxygen. During glycolysis, glucose is broken down into pyruvate, and then pyruvate is transformed into ethanol and carbon dioxide.

The production of carbon dioxide is a key feature of alcoholic fermentation; it's responsible for the bubbles in carbonated beverages and contributes to the rising of bread when yeast ferments the sugars in the dough. Therefore, the correct answer highlights the byproduct of this fermentation process alongside ethanol.

The other options do not relate to the products of alcoholic fermentation: oxygen is not produced as fermentation is anaerobic; lactic acid is produced during lactic acid fermentation, which occurs in muscle cells under low oxygen conditions; and glycerol is not a direct product of alcoholic fermentation but can occasionally be involved in other metabolic pathways.