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: Angiofibroma is a benign, vascular, locally invasive tumor. It has a fibrous stroma with irregular vascular channels, lined by endothelial cells without elastic membrane. Smooth muscle are often absent or incompletely present in it due to which it has tendency to bleed profusely. It is usually found in adolescent boys between ages of 10 and 17 years. Patients presents with symptoms of nasal obstruction and epistaxis in localized tumors. It usually originates in the posterolateral aspect of the nasal cavity. CT is the best method for diagnosing it.', 'role': 'assistant'}]