Concept:Zymase is the enzyme present in yeast that catalyses the alcoholic fermentation of glucose.Explanation:Glucose is converted into ethanol and carbon dioxide in the absence of oxygen.The reaction is:C6H12O6zymase2C2H5OH+2CO2This anaerobic breakdown is brought about by zymase.Diastase acts on starch, maltase acts on maltose, and ptyalin acts on starch in the mouth.None of these produces ethanol and carbon dioxide from glucose.Answer:D. zymase