Final answer:
A. SVC and IVC
The veins that return blood directly to the right atrium are the superior vena cava (SVC) and the inferior vena cava (IVC), making A. SVC and IVC the correct answer.
Step-by-step explanation:
The veins that return blood directly to the right atrium (RA) of the heart are the superior vena cava (SVC) and inferior vena cava (IVC). The SVC returns blood from the body regions above the diaphragm, including the head, neck, chest, shoulders, and upper limbs. Additionally, the subclavian vein forms on both the left and right sides when the axillary vein passes through the body wall, contributing to the brachiocephalic vein that, in turn, drains into the SVC. The IVC returns blood from the regions below the diaphragm, which includes the abdominal and pelvic regions and the lower limbs.
Based on these facts, the answer to the question of which veins return blood directly into the right atrium is A. SVC and IVC.
The options such as the pulmonary veins, femoral vein, subclavian vein, and an interjugular vein (not a standard anatomical term) are incorrect. Pulmonary veins return oxygen-rich blood from the lungs to the left atrium, not to the right atrium. The femoral vein and others eventually drain into the systemic venous circulation but not directly into the right atrium.