The correct answer is: Gasoline.
Gasoline has the highest fuel value because it is a hydrocarbon, which means it is made up of hydrogen and carbon atoms. When gasoline is burned, the hydrogen and carbon atoms combine with oxygen in the air to form water and carbon dioxide. This reaction releases a lot of energy, which is why gasoline is such a good fuel.
Hydrogen is also a hydrocarbon, but it has a higher fuel value than gasoline. However, hydrogen is difficult to store and transport, which is why it is not as widely used as a fuel.
Charcoal is made up of carbon, which is why it has a high fuel value. However, charcoal does not release as much energy as gasoline when it is burned.
Natural gas is a mixture of hydrocarbons, including methane, ethane, and propane. It has a lower fuel value than gasoline, but it is still a good fuel.
In conclusion, gasoline has the highest fuel value because it is a hydrocarbon that releases a lot of energy when it is burned.