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': 'Co-60 units: \nSelect and explain. \nA. g radiation, B. b radiation, C. a, and b radiation, D. a, b and g radiation', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Ans. g radiation', 'role': 'assistant'}]