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
Which amongst the following have largest half-life? 
Select and explain. 
A. Radon, B. Radium, C. Plutonium, D. Iridium
B: Radium
Answer: B: Radium 
Explanation: Radium REF: APPENDIX-67 for "ISOTOPES USED IN RADIOTHERAPY" "Radium has maximum half-life of 1622 years"