The correct option is B cellular respiration
∙ Digestion breaks down the complex carbohydrates into simple glucose units. The glucose molecules are further broken down to release energy in respiration.
∙ During cellular respiration, glucose is further broken down into carbon dioxide and water with the help of oxygen and energy is released in the form of ATP.
∙ Circulatory system performs the function of transporting various substances like water, hormones, oxygen, etc. Excretion refers to the elimination of waste products from the body.