In gaseous form N2O5 dissociate as: 2N2O5→4NO2→O2 hence (a) is incorrect.In solid form N2O5 is ionic, hence (b) is correct.There are both covalent and coordinate covalentbonds, hence (c) is incorrect. It is a colourless compound, hence (d) isincorrect. So, statement (b) is correct for dinitrogen petoxide.