(a) : In alcohol fermentation triose phosphate is the electron donor while acetaldehyde is the electron acceptor.
(In alcoholic fermentation, the pyruvic acid from glycolysis loses one carbon in the form of carbon dioxide to form acetaldehyde, which is reduced to ethyl alcohol by NADH. When acetaldehyde is reduced to ethyl alcohol, NADH becomes NAD+ (is oxidized). This is the fermentation that commonly occurs in yeast.)