The answer is Fiber.
Fiber is added to the food just so that it can stimulate the movement of our intestine so that digestion can happen easier. Basically when fiber meets water, it expands and therefore stimulates peristalsis in intestines as it touches the wall of it and so that constipation can be prevented.
Fiber is not absorbed by body meanwhile all the other choices are. Amino acids is the simple form of protein, it is needed to make structures like DNA. Fatty acids is the simple form of lipids, it can help develop organelles like cell membrane. Sugar is the main source of energy and vitamins can help prevent different illness such as vitamin c can prevent anaemia while d can increase the absorption of calcium so ricket can be prevented.
