Answer: A - Venous blood vesselsreturn blood from the body to the heart.
An exception is the pulmonary vein, which provides oxygenated blood to the heart from the lungs for circulation to the body. Like arteries, veins graduate in size as they return to the heart.The smallest veins, venules, begin the bloods' return to the heart at the capillary network. The largest veins are nearest the heart. Unlike arteries, venous walls contain very little muscle fiber and lack the elasticity found in arterial walls. Instead, venous blood vessels contain one-way valves that allow blood to flow in one direction only-towards the heart.
