immune and excretory digestive and respiratory nervous and skeletal circulatory and integumentary
I gave my students this multiple choice question: When a soccer player kicks a ball, which two systems work directly with the muscular system?

Only one answer is correct among these 4 choices:
- immune and excretory
- digestive and respiratory
- nervous and skeletal
- circulatory and integumentary

Could you tell me which one is correct?

nervous and skeletal