The heart removes waste built up in the lungs. Oxygen enters the bloodstream directly from the nose. Oxygen is transferred to the bloodstream as blood passes by the lungs. The heart pumps air into the blood through the lungs.
I gave my students this multiple choice question: Which best describes how the human circulatory and respiratory systems interact?

Only one answer is correct among these 4 choices:
- The heart removes waste built up in the lungs.
- Oxygen enters the bloodstream directly from the nose.
- Oxygen is transferred to the bloodstream as blood passes by the lungs.
- The heart pumps air into the blood through the lungs.

Could you tell me which one is correct?

Oxygen is transferred to the bloodstream as blood passes by the lungs.