For fuel to be useful, energy must be released a. as heat or light b. in a controlled way c. contimuously d. over a long period of time

B.in a controlled way

Explanation:

Fuels are all chemicals that, when reacting with oxygen (O2), undergo a chemical phenomenon called combustion, releasing a certain amount of energy in the form of heat. This energy must be released in a controlled manner, avoiding accidents and waste.

Every burning of a fuel is an exothermic (heat-releasing) chemical reaction, but the products that originate always vary according to the fuel used. Fuels can generally come from a variety of sources, such as animal, vegetable, water hydrolysis or waste. Regardless of origin, for fuel to be useful, energy must be released in a controlled manner.

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