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
Half life of I131 is 
Select and explain. 
A. 4 hours, B. 8 days, C. 4 days, D. 10 days
B: 8 days
Answer: B: 8 days 
Explanation: B i.e. 8 days