Answer:
First Option
Step-by-step explanation:
When you consume food and it goes through your digestive system your body takes a good amount of the good and converts it into energy and distributes it throughout your body leaving the rest of the food as waste then it will soon leave the body in it's own way as it reaches the end of the digestive cycle. In this case the animal consumed food and then the body converted it into energy causing the animal to gain mass or "grow."
Hope this helps