The correct answer is coal, oil and water. Coal is a wise source of energy as it is the cheapest source of energy. Edwin L. Drake's was the first american to drill oil and then later oil was modified to be used as a source of energy. Oil as a source of energy is a viable option as it has a high energy density within it. Lastly, Water energy is used with hydro-power. Water is used as it is a clean fuel source.
~Haily
