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': 'Which amongst the following have largest half-life? \nSelect and explain. \nA. Radon, B. Radium, C. Plutonium, D. Iridium', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Radium REF: APPENDIX-67 for "ISOTOPES USED IN RADIOTHERAPY" "Radium has maximum half-life of 1622 years"', 'role': 'assistant'}]