Answer: I believe it is D, the Nervous System.
Explanation:
Systematic separation of the circulation of the blood. The right side of the heart receives oxygen-poor blood from your body and pumps it to the lungs. The lungs oxygenate the blood which returns to the heart and is pumped to the rest of the body by the left side of the heart. After which the blood returns to the right side, completing the cycle of circulation.
The answer is apex and base. To simplify, the apex of the heart rests on the diaphragm and from its base, the great vessels emerge. In addition, blood vessels that are nearer to the pumping heart and must enlarge to endure pressure variations are named elastic arteries and foramen ovale permits blood to pass from the right to the left atrium, therefore avoiding to pass the fetal lungs.
