In question B, starch is hydrolyzed to produce glucose, which is decomposed to produce ethanol under anaerobic conditions, and ethanol is eliminated to produce ethylene. Ethylene and bromine are added to produce 1, 2- dibromoethane, which is hydrolyzed to produce ethylene glycol and then oxidized to produce oxalic acid, so there are no hydrogenation, esterification and addition polymerization reactions.