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': 'Radiotherapy is used in treatment of angiofibroma when it involves: \nSelect and explain. \nA. Cheek, B. Orbit, C. Middle cranial fossa, D. Cavernous sinus', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Radiotherapy is useful only for advanced cases of the tumor, when there is intracranial extension.', 'role': 'assistant'}]