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': 'Production of X-ray is mainly contributed by: \nSelect and explain. \nA. Brehmstalung radiation., B. Characteristic radiation., C. Both., D. None.', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Production of X-Ray', 'role': 'assistant'}]