Which structure receives blood from the lower limbs and abdomen and empties into the right atrium of the heart?

The inferior vena cava is the correct answer because it specifically functions as the large vein that collects deoxygenated blood from the lower parts of the body, including the lower limbs and the abdominal region. It channels this blood directly into the right atrium of the heart, facilitating the return of systemic blood to the heart so that it can be pumped to the lungs for oxygenation.

In contrast, the superior vena cava collects blood from the head, neck, and upper extremities, which is why it does not serve the lower limbs and abdomen. The aorta, on the other hand, is responsible for distributing oxygenated blood from the heart to the rest of the body, while the pulmonary vein carries oxygenated blood from the lungs back to the left atrium of the heart. Thus, the unique role of the inferior vena cava makes it the correct structure responsible for receiving blood from the specified regions of the body and delivering it to the heart.