Final answer:
Veins are part of the body system that transport blood back to the heart after it has circulated through the body. The correct option is A.
Step-by-step explanation:
The part of the body system that transports blood to the heart is veins. The circulatory system is composed of the heart, arteries, veins, and capillaries.
Arteries are the vessels that carry blood away from the heart to the rest of the body, supplying oxygenated blood to various tissues. After the exchange of gases, nutrients, and waste products in capillaries, deoxygenated blood is carried back to the heart through veins.
Venous blood flow is facilitated by valves that prevent the backflow of blood, ensuring the blood moves in the correct direction towards the heart.