The only type of vein in the body which carries oxygenated blood is _________.

The pulmonary vein is unique in the vascular system because it is the only vein that carries oxygenated blood. Typically, veins carry deoxygenated blood back to the heart, as they are responsible for returning blood that has circulated through the body and has had oxygen extracted by the tissues. However, the pulmonary veins transport blood from the lungs, where it has picked up oxygen during the process of respiration, back to the left atrium of the heart. This oxygen-rich blood is then pumped out to the body through the aorta.

In contrast, other types of veins mentioned have different functions. The femoral vein, for example, brings deoxygenated blood from the lower extremities back to the heart. The jugular vein is responsible for draining blood from the head and neck, and it also carries deoxygenated blood. Systemic veins collect blood from various parts of the body that is low in oxygen and transport it towards the heart. Thus, the pulmonary vein stands out as the exception among veins due to its role in oxygenation, making it the correct choice.