the digestive system and the circulatory system the circulatory system and the respiratory system the respiratory system and the skeletal system the skeletal system and the digestive system
I gave my students this multiple choice question: Bone cells need nutrients. Which two systems get nutrients to bone cells?

Only one answer is correct among these 4 choices:
- the digestive system and the circulatory system
- the circulatory system and the respiratory system
- the respiratory system and the skeletal system
- the skeletal system and the digestive system

Could you tell me which one is correct?

the digestive system and the circulatory system