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
Azygos vein - 
Select and explain. 
A. Formed by arch of aorta, B. Opens into inferior vena cava, C. Arches the groove of the left lung, D. Ascends through the aortic opening in the diaphragm
D: Ascends through the aortic opening in the diaphragm
Answer: D: Ascends through the aortic opening in the diaphragm 
Explanation: Azygos vein is formed by

Subcostal veins
Ascending lumbar veins
Lumbar Azygos veins

It crosses the diaphragm on the right side, by piercing the right crus or the aortic opening.
At the level of T4 vertebra, it arches over the hilum of right lung.
It opens into the superior vena cava.