<h2>The correct answer is: A. Veins cannot prevent the backflow of blood. </h2>
Explanation:
Blood, the fluid connective tissue, conducts nutrients and oxygen to the cells of the body and removes waste products and carbon dioxide from the cells of the body through blood vessels called Arteries and Veins.
The Arteries carry oxygenated blood from the heart to all the parts of the body (except pulmonary artery) while the Veins carry deoxygenated blood from all the parts of the body to the heart (except pulmonary vein).
Arteries have thick muscular wall with narrow lumen and are devoid of valves. Blood flows in huge pressure through them. They remain deep seated in the body.
Veins have thinner muscular wall with wider lumen. They have valves to maintain unidirectional blood flow and prevent the backflow of blood because the pressure applied by the blood on the walls of the veins is lower than arteries. Veins are superficially situated in the body.
Varicose vein is a disease condition characterized by the swelling and twisting of veins and abnormal functioning of the valves of the veins. As a result of this, the backflow of blood in the vein cannot be prevented, thereby causing pain.
