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': 'Half-life of Iodine 131 is \nSelect and explain. \nA. 8 hours, B. 8 days, C. 8 weeks, D. 8 months', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Iodine 131 is a radioisotope with a very short half-life of 8.02 days, making it highly radioactive. Frequently used in small doses in thyroid cancers therapies, it is also one of the most feared fission products when accidentally released into the environment', 'role': 'assistant'}]