Conversion of pyruvic acid into CO2, acetaldehyde and NADH is catalysed by
Alcohol dehydrogenase
Pyruvate decarboxylase
Pyruvate dehydrogenase
Alcohol decarboxylase
The first reaction of alcohol fermentation i.e. conversion of pyruvic acid into CO2, acetaldehyde and NADH catalyzed by pyruvate decarboxylase.
hence, the correct option is b.