Energy Tech

Consider the following statements regarding energy forms and conversion:

I. Electrical energy is a secondary energy source derived from the conversion of primary sources like coal, natural gas, or sunlight.

II. The law of conservation of energy states that energy can neither be created nor destroyed, but can be transformed from one form to another.

III. In any energy conversion process, the total useful energy output is always equal to the total energy input.

How many of the statements given above are correct?