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': 'During the production of X-rays, how much of electron energy is converted into heat \nSelect and explain. \nA. 99%, B. 94%, C. 89%, D. 84%', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]