The options you've provided all contain valid benefits of eating food for animals, but if you are looking for which one is not the best answer regarding the primary purpose of eating food, it would be "The animal gets heat from the food."
While animals can generate heat through metabolic processes that convert food into energy, the direct benefits of eating are more accurately reflected in gaining raw materials, water, and energy. Thus, "The animal gets heat from the food" is the least direct benefit compared to the others.