This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Vasculitis, Subject name: Pathology
Hypersensitivity vasculitis most commonly involves: 
Select and explain. 
A. Aerioles, B. Post-capillary venules, C. Capillaries, D. Medium sized aeries
B: Post-capillary venules
Answer: B: Post-capillary venules 
Explanation: Post capillary venules are the most commonly involved vessels; capillaries and aerioles may be involved less frequently.