help eliminate body wastes. help blood circulate. aid in digestion. aid in respiration.
I gave my students this multiple choice question: The skin, lungs, and kidneys work together to

Only one answer is correct among these 4 choices:
- help eliminate body wastes.
- help blood circulate.
- aid in digestion.
- aid in respiration.

Could you tell me which one is correct?

help eliminate body wastes.