Final answer:
Pulmonary veins transport oxygenated blood from the lungs back to the left atrium of the heart. They are part of the pulmonary circulation and are the only veins that carry oxygen-rich blood.
Step-by-step explanation:
The pulmonary veins are crucial vessels within the pulmonary circulation that are responsible for carrying oxygenated blood from the lungs back to the heart. More specifically, they return this blood to the left atrium of the heart, not the right atrium as systemic veins do.
The right ventricle, on the other hand, pumps deoxygenated blood away from the heart and through the pulmonary trunk and pulmonary arteries to the lungs. After the blood becomes saturated with oxygen in the pulmonary capillaries, the pulmonary veins carry this oxygen-rich blood back to the heart.
Therefore, the correct answer to the question 'Pulmonary veins: _______' is B) transport oxygenated blood to the heart.