Concept:Concentrated tetraoxosulphate(VI) acid, H2SO4, is a strong dehydrating agent that removes water from carbohydrates, leaving carbon.Explanation:Glucose, C6H12O6, contains hydrogen and oxygen in the ratio of water.When heated with concentrated H2SO4, the acid removes the elements of water from glucose.The dehydration reaction is: C6H12O6conc. H2SO46C+6H2OTherefore, black carbon residue is formed.The other options, carbon(IV) oxide, ethane, and ethanol, are not dehydration products of glucose under these conditions.Answer:A. carbon