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: Radiology
[{'content': 'Pericardial calcification is caused by all except \nSelect and explain. \nA. Radiotherapy to the mediastinum, B. Methysergide therapy, C. Anticoagulant therapy, D. Benign pericarditis', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Ans. Radiotherapy to the mediastinum', 'role': 'assistant'}]