For this question, what you need to pay attention to is what the process of photosynthesis does for the plant, once you know that, the answer is pretty much over.
Being brief, the photosynthesis uses the light to create energy, and this energy is used to maintain the metabolism working in a way that the plant won't miss this energy. So, this process creates a molecule called glucose, that's the energy for the plant, and it's used for many functions within it. For example, plants use glucose to make cellulose, the main part of their cell wall. Starch is too, made by using glucose, and it's used as a reservation of energy for the plant.
