I think these are the substances that are needed to be categorized into ionic, metallic or covalent: C2H6, Na2O, SiO2, CO2, N2O5, NaNO3, Al, C (diamond) and SO2. Ionic substances are Na2O, SiO2, NaNO3; covalent substances are C2H6, CO2, N2O5, C (diamond); and metallic substances are Al, SO2.
