The correct answer is (a) Helps in deciding which fuel is good
The explanation: The different fuels have different calorific values, i.e. different fuels produce different amount of heat in heat on burning. The calorific value of fuel helps us to decide that which fuel is good for us. This is done by comparing the calorific values of fuels with each other. Usually, a fuel having higher calorific value is considered to be a good fuel.