Answer the following question given this paragraph: 

The veins that return oxygen-poor blood to the heart are the superior vena cava and the inferior vena cava . The pulmonary veins return oxygen-rich blood from the lungs to the heart. The pulmonary veins are the only veins that carry oxygen-rich blood.


Q: The superior vena cava and the inferior vena cava are veins that return blood lacking what to the heart?

 Choices:

- hemoglobin

- carbon dioxide

- nitrogen

- oxygen

A:
oxygen
