Final answer:
Veins allow blood to return to the heart by transporting blood back to the heart, while arteries carry blood away from the heart. Both veins and arteries have valves to prevent the backflow of blood.
Step-by-step explanation:
Veins allow blood to return to the heart. Blood pumped by the heart flows through a series of vessels, including arteries, arterioles, capillaries, venules, and veins, before returning to the heart. Arteries transport blood away from the heart, while veins bring blood back to the heart. Both veins and arteries have valves to prevent the backflow of blood.