What are important products of yeast fermentation?

The correct option is C All of the above

• Fermentation is a metabolic process that converts sugar to acids, gases or alcohol anaerobically. It occurs in yeast and bacteria, but also in oxygen-starved muscle cells, as in the case of lactic acid fermentation.
  
• By fermentation, the yeast species Saccharomyces cerevisiae converts carbohydrates to carbon dioxide, acetic acid and alcohols like ethanol, butanol, phenethyl and amyl alcohol.

• Yeast produces carporic acid by the fermentation of corn.

Thus, the correct answer is option D.