Final answer:
The false statement about the circulatory system is that blood in the pulmonary vein is deoxygenated. In fact, this blood is oxygenated as it returns from the lungs, where gas exchange has occurred.
Step-by-step explanation:
The mammalian circulatory system includes two main circuits: the pulmonary circuit and the systemic circuit. The pulmonary circuit is responsible for gas exchange, as it transports deoxygenated blood to the lungs to pick up oxygen and release carbon dioxide, and then returns oxygenated blood to the heart. As for the systemic circuit, it distributes this oxygenated blood to the rest of the body.
In response to the student's question, the false statement is: a. Blood in the pulmonary vein is deoxygenated. In fact, blood in the pulmonary vein is oxygenated, as it comes from the lungs after the exchange of gases has taken place. The other statements are true: blood in the inferior vena cava is deoxygenated as it returns to the heart from the body, blood in the pulmonary artery is deoxygenated as it is being transported to the lungs, and blood in the aorta is indeed oxygenated as it is distributed to the body from the heart.