Correct Answer: Pulmonary Vein

Solution : The correct answer is pulmonary vein.

Pulmonary vein carry clean blood from lungs to heart. Although veins carry impure blood from body organs to heart but pulmonary vein carries pure blood from lungs to heart and from there arteries carries it to various parts of body. On the contrary pulmonary artery carries impure blood from heart to lungs. This system of circulation is known as pulmonary circulation.