circulatory and skeletal systems skeletal and excretory systems muscular and circulatory systems respiratory and muscular systems
I gave my students this multiple choice question: Which pair of systems is responsible for the flow of blood in the human body?

Only one answer is correct among these 4 choices:
- circulatory and skeletal systems
- skeletal and excretory systems
- muscular and circulatory systems
- respiratory and muscular systems

Could you tell me which one is correct?

muscular and circulatory systems