Concept:Boiling a liquid only breaks the weak forces between molecules, not the strong covalent bonds inside each molecule.Explanation:Ethanol (C2H5OH) molecules attract one another through hydrogen bonds in the liquid state.When ethanol is boiled, enough energy is supplied to break these intermolecular hydrogen bonds.Breaking these bonds allows ethanol molecules to escape as vapour.The covalent bonds within each ethanol molecule remain intact during boiling.Ethanol does not contain ionic bonds, so no ionic bonds are involved.Answer:C. III only