Final answer:
Oxygen-poor blood is found in the pulmonary arteries and systemic veins. Pulmonary arteries carry deoxygenated blood to the lungs, while systemic veins return it to the heart.
Step-by-step explanation:
Oxygen-poor blood can be found in the pulmonary arteries and the systemic veins. The pulmonary arteries carry deoxygenated blood from the heart to the lungs for oxygenation. Conversely, the systemic veins return deoxygenated blood from the body to the heart after the tissues have used up the oxygen delivered by the systemic arteries.
Specifically, the inferior vena cava and the superior vena cava are the veins that return oxygen-poor blood to the heart. It is important to remember that the pulmonary veins are the only veins that carry oxygen-rich blood from the lungs back to the heart, contrasting with the other veins in the body.