Question

lo 3.3. what do veins carry back to the heart?
waste products
oxygenated blood
carbon dioxide
nutrients
deoxygenated blood

Explanation:

Veins are blood vessels that carry blood back to the heart. In the systemic circulation, veins carry deoxygenated blood (which has delivered oxygen to the body's tissues) back to the heart. While there are exceptions like the pulmonary veins (which carry oxygenated blood from the lungs to the heart), generally, the main function of veins in the body's general circulation is to return deoxygenated blood. Waste products are removed by excretory organs like the kidneys and lungs in a more complex process involving the blood but not specifically just carried by veins as their main identity. Oxygenated blood is mainly carried by arteries (again, pulmonary arteries are an exception as they carry deoxygenated blood to the lungs). Carbon dioxide is a waste gas that is transported in the blood (in part as bicarbonate ions etc.) but veins' main categorization is based on the oxygen - content of the blood they carry. Nutrients are absorbed into the blood (e.g., in the intestines) and transported throughout the body, but not the key defining feature of veins.

Answer:

Deoxygenated blood