Enzymatic conversion of glucose to ethanol is

Fermentation is the biochemical process in which enzymes (particularly zymase, found in yeast) convert glucose into ethanol and carbon dioxide. The overall equation is:

\[\text{C}_6\text{H}_{12}\text{O}_6 \xrightarrow{\text{zymase}} 2\text{C}_2\text{H}_5\text{OH} + 2\text{CO}_2\]

This is an anaerobic process, meaning it occurs without oxygen. The key word in the question is enzymatic, which points directly to fermentation, since it is the only process among the given options that is enzyme-catalysed.

Polymerization is the joining of small monomer molecules into a large polymer chain. Hydrogenation is the addition of hydrogen gas across unsaturated bonds, typically using a metal catalyst such as nickel. Saponification is the alkaline hydrolysis of fats or oils to produce soap and glycerol. None of these processes involves the enzymatic breakdown of glucose to ethanol.

Whenever a question mentions the biological or enzymatic conversion of sugars to alcohol, the answer is fermentation.