The correct option is C Respiration.
In all living organisms including plants energy is released by the process of respiration. Respiration is chemically an oxidative process in which reduced substrates (carbohydrates, fats and amino acids) are oxidised and energy is released. All oxidative steps in the degradation of carbohydrates, fats and amino acids converge at the final stage of cellular respiration, in which the energy of oxidation drives the synthesis of ATP.