Answer:
Food
Step-by-step explanation:
Animals obtain energy when they eat. So do we, because we have animal cells! If you don't eat you will get weak and your body needs the nutrients that it gets from the food that you eat. So to make adenosine triphosphate (ATP), you need energy and some other factors that go into making ATP.. but that is the just of it.
You need food.
Hope this helps!