Answer:
In digestion molecules come from food the animal eats (option a).
Step-by-step explanation:
Foods that are consumed are those that provide the necessary molecules for the maintenance of the organism. The process of digestion consists of converting food into molecules —amino acids, glucose and fatty acids— that are easily absorbed by the body.
When an animal eats food, its digestive system is in charge of processing it and converting it into simple molecules, necessary to cover its requirements.