C. in the respiration equation, does energy act as a reactant or a product? explain.

In the respiration equation, the energy act as a "product" because the energy is generated from the oxidation of the stored molecule which is glucose.  

Explanation:  

During photosynthesis the energy act as a reactant to generate sugar molecules but during respiration the produced sugar molecule is used to produce energy through oxidative phosphorylation. Hence, during the respiration energy acts as a product rather than a reactant because the product of respiration is ATP molecule which is a high energy product of respiration.

air enters through the nose, moves through the nasal cavity, the pharynx, the larynx, enters the trachea, moves through the bronchi andbronchioles till the alveoli.