This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Physics of Radiotherapy, Subject name: Radiology
[{'content': 'Radioiodine 131 half life: \nSelect and explain. \nA. 8 days, B. 15.7 days, C. 74.3 days, D. 13 hours', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Ans. (a) 8 daysRef: Basics radiological physics 2nd ed. /180* Iridium-192, emits gamma rays. It has energy of 0.4MeV.* Tl/2 of iridium 192: 74 daysImportant Half Life of Radionuclides* Gold-198: 2.7 days* Iodine- 123: 13.3 hours* Iodine-131: 8 days* Phosphorus-32: 14.3 days* Yttrium 90: 64 hours* Cobalt-60: 5.26 years* Caesium-137: 30 years* Radium-226: 1620 years', 'role': 'assistant'}]