break down foods for absorption into the blood exchange oxygen and carbon dioxide in the lungs release energy from sugars within the cells carry nutrients to all parts of the body
I gave my students this multiple choice question: The main function of the human digestive system is to

Only one answer is correct among these 4 choices:
- break down foods for absorption into the blood
- exchange oxygen and carbon dioxide in the lungs
- release energy from sugars within the cells
- carry nutrients to all parts of the body

Could you tell me which one is correct?

break down foods for absorption into the blood