The correct statements among (a) to (d) regarding H₂ 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 NaNi₅.

(d)   On combustion, values of energy released per gram of liquid dihydrogen and LPG are 50 and 142 KJ, respectively.

NaH is an example of :

The total number of isotopes of hydrogen and number of radioactive isotopes among them, respectively, are :

The chemical nature of hydrogen peroxide is :