The correct statements among (a) to (d) regarding $\mathrm{H}_2$ as a fuel are
(a) It produces less pollutants than petrol.
(b) A cylinder of compressed dihydrogen weighs $\sim 30$ times more than a petrol tank producing the same amount of energy.
(c) Dihydrogen is stored in tanks of metal alloys like $\mathrm{NaNi}_5$.
(d) On combustion, values of energy released per gram of liquid dihydrogen and LPG are 50 and 142 kJ , respectively.