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': 'Most harmful to individual cell : \nSelect and explain. \nA. X-rays, B. a - paicles, C. b - paicles, D. X- rays (gamma rays)', 'role': 'user'}, {'content': 'Answer: B \nExplanation: B i.e. a - paicles', 'role': 'assistant'}]