Step 1: Begin by understanding the key terms provided in the question. 'Fermentation' refers to a metabolic process that converts sugar to acids, gases, or alcohol in the absence of oxygen. 'Photosynthesis' is the process by which plants convert light energy into chemical energy. 'Diffusion' is the passive movement of molecules from an area of higher concentration to an area of lower concentration. 'Metabolism' encompasses all chemical reactions in the body that maintain life, including the intake and use of food.