Concept:Arteries and veins differ in structure, direction of blood flow, lumen size, and valves.
Explanation:Arteries carry blood away from the heart, while veins carry blood toward the heart.
Arteries have thick muscular walls and a relatively narrow lumen.
Veins have thinner walls and a relatively wide lumen.
Veins have valves to prevent backflow of blood; arteries do not have valves.
Arteries generally carry oxygenated blood, and veins generally carry deoxygenated blood, with exceptions like the pulmonary vessels.
So the correct distinction from the options is that arteries have a relatively narrow lumen while veins have a relatively wide lumen.
Answer:A. Arteries have relatively narrow lumen while veins have relatively wide lumen.