Which one of the following has the highest fuel value ?

Calorific value (energy per unit mass) shows hydrogen has the highest fuel value by a large margin. Typical higher heating values are: hydrogen ≈ 141.7 MJ/kg; natural gas (methane) ≈ 52 MJ/kg; gasoline (gasoil) ≈ 43 MJ/kg; and charcoal ≈ 29.6 MJ/kg. These standard heating-value figures demonstrate that, on a mass basis, hydrogen contains substantially more chemical energy than the other listed fuels, so hydrogen is the highest fuel value among the options.