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: ENT
[{'content': 'Angiofibroma bleeds excessively because - \nSelect and explain. \nA. It lacks a capsule, B. Vessels lack a contractile component, C. It has multiple sites of origin, D. All of the above', 'role': 'user'}, {'content': 'Answer: B \nExplanation: The characteristic of JNA is that the vessels are just endothelial - lined spaces with no muscle coat.\nAs the contractile component (muscle coat) of vessels is absent, vessels have no ability to contract, i.e. vasoconstriction does not occur, and this accounts for :-\n\n\nSevere and recurrent epistaxis\nBleeding cannot be controlled by application of adrenaline, a potent vasoconstrictor.', 'role': 'assistant'}]