PATHOLOGY

Detailed explanation-1: -Veins comprise valves, which prevent the backward flow of the blood. The valves are bicuspid, that is, they comprise two flap-like compositions. In the veins, the valves ensure that the flow of blood takes place only in one direction. On the other hand, arteries carry oxygenated blood away from the heart.

Detailed explanation-2: -The valves open, allowing the blood to flow, and close, stopping the blood from flowing backwards. After running through this network of veins, blood reaches the heart and travels to the lungs, which supply it with oxygen and allow it to expel carbon dioxide and other waste.

Detailed explanation-3: -So, the correct option is ‘Veins’.