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': 'Radioactive element not used now-a-days in medical practice: \nSelect and explain. \nA. Radium 226, B. Co60, C. Cs 137, D. Iridium 192', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Ans. Radium 226', 'role': 'assistant'}]