How is alcohol produced?

Alcohol is produced primarily through the process of fermentation, which involves the conversion of sugars into alcohol and carbon dioxide by yeast. During fermentation, yeast consumes sugars and, as a byproduct of this metabolic process, ethanol (alcohol) is produced along with carbon dioxide. This is the fundamental reaction that underpins the production of alcoholic beverages such as beer, wine, and distilled spirits, making fermentation the correct answer.

The process of fermentation harnesses the natural abilities of yeast, which is a microorganism capable of metabolizing sugars without the need for air. This anaerobic process directly links sugar sources, such as fruits, grains, or other carbohydrate-rich materials, to the formation of alcohol.

In contrast, the other options do not accurately represent how alcohol is produced. For example, condensation of water does not relate to alcohol production, as it refers to the physical change from gas to liquid state. Filtration of starch involves separating solid particles from liquids, which does not lead to alcohol. Oxidation of yeast describes a metabolic process where energy is produced in the presence of oxygen, but it does not directly contribute to the production of alcohol as fermentation does. Thus, fermentation of sugar stands out as the essential and correct method of alcohol production.