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': 'X-rays are formed when electrons hit: \nSelect and explain. \nA. Water, B. Anode, C. Radium source, D. None of the above', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Ans. Anode', 'role': 'assistant'}]