This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Thorax, Subject name: Anatomy
Right superior intercostal vein drains into 
Select and explain. 
A. Brachiocephalic vein, B. Azygos vein, C. Inferior venacava, D. Hemizygos vein
B: Azygos vein
Answer: B: Azygos vein 
Explanation: The right superior intercostal vein drains the 2nd, 3rd, and 4th posterior intercostal veins on the right side of the body. It flows into the azygos vein. The left superior intercostal veins drains the 2nd and 3rd posterior intercostal veins on the left side of the body. It drains into the left brachiocephalic vein B D CHOURASIAS HUMAN ANATOMY UPPER LIMB THORAX VOLUME, 1 SIXTH EDITION, page no,221