The correct answer is Hydrogen.

Let`s dissect each option for better understanding:

Option 1 - Hydrogen: Hydrogen has the highest energy content per mass among fuels, hence it has the highest fuel value. It gives off about 142 MJ/Kg, which is almost three times that of gasoline.

Option 2 - Charcoal: Charcoal commonly gives off 30 MJ/kg, significantly less than hydrogen. While charcoal is a good source of heat, it doesn`t compare to Hydrogen in terms of fuel value.

Option 3 - Natural gas: Natural gas has a energy content of around 55 MJ/Kg. Higher than Charcoal but still less than half of that of Hydrogen.

Option 4 - Gasoline: Gasoline is a common fuel for cars and gives off about 46 MJ/Kg. This is more than Charcoal and Natural gas, but still less than Hydrogen.

So, when we compare the energy content per Kg of these options, Hydrogen stands out as the one with the highest fuel value.