Oil layer excludes oxygen in anaerobic fermentation

Steps:

• Fermentation by yeast produces alcohol under anaerobic conditions.
• Oxygen presence allows yeast to perform aerobic respiration instead, oxidizing alcohol.
• The oil layer floats on the mixture, forming a barrier against air.
• This ensures oxygen exclusion, promoting alcohol fermentation.

Why B is correct:

• Fermentation is defined as anaerobic respiration in yeast, yielding ethanol and CO2; oil prevents oxygen entry, blocking aerobic respiration (C6H12O6 → 2C2H5OH + 2CO2).

Why the others are wrong:

• A: Alcohol dissolves naturally in the aqueous solution; oil does not retain it.
• C: Carbon dioxide is a byproduct of yeast metabolism, not produced by oil.
• D: Oil is inert and provides no nutrients; yeast uses sugars in the mixture.

Final answer: B