This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Anatomy
Azygous vein drains into: 
Select and explain. 
A. Right subcostal vein, B. Superior vena cava, C. Braciocephalic, D. Right ascending lumbar vein
B: Superior vena cava
Answer: B: Superior vena cava 
Explanation: The origin of the azygos vein is variable. It is often formed by the union of the right ascending lumbar vein and the right subcostal vein.It ascends through the aoic opening in the diaphragm on the right side of the aoa to the level of the fifth thoracic veebra.Here it arches forward above the root of the right lung to empty into the posterior surface of the superior vena cava. The azygos vein has numerous tributaries, including the fifth to eleventh right posterior intercostal veins, the right superior intercostal vein, the hemiazygos and the accessory hemiazygos veins, and numerous esophagral, mediastinal and pericardial veins.