Final answer:
Systemic blood leaves the heart through the aorta and returns to the right atrium via the superior vena cava, inferior vena cava, and the coronary sinus.
Step-by-step explanation:
The correct answer to the question is a) Aorta. Systemic blood, which is oxygenated blood after returning from the pulmonary circuit, is pumped from the left atrium into the left ventricle, which then pumps it into the aorta. The aorta is the body's largest artery, and it branches out to supply oxygenated blood to the entire body. After oxygen is used by the body's tissues, deoxygenated blood returns to the heart via systemic veins, primarily the superior vena cava (collecting blood above the diaphragm), the inferior vena cava (collecting blood below the diaphragm), and the coronary sinus (draining the blood from the heart muscle), which all empty directly into the right atrium. Therefore, blood leaves the heart through the aorta and returns via the superior vena cava, the inferior vena cava, and the coronary sinus.