This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Radiotherapy beam production, Subject name: Radiology
The T 1/2 of iodine 131 is: 
Select and explain. 
A. 13 days, B. 8 days, C. 2 days, D. 12 hours
B: 8 days
Answer: B: 8 days 
Explanation: Ref: Internet SourcesExplanation:The t1/2 of iodine 131 is 8 daysHalf life's of commonly used radioisotopes in MedicineIsotopeHalf lifeAmericium- 241433 yearsAntimony-12460.2 daysCalifornium-2522.63 yearsCesium-13730.1 yearsCobalt-57271 daysCobalt-5871.3 daysCobalt-605.272 yearsIodine-1244.17 daysIodine-13012.4 hoursIodine-1318.041 daysIron-528.3 hoursIron-552.7 yearsIron-5944.6 daysManganese-525.63 daysManganese-54312.5 daysMolybdenum-9966.02 hoursOsmium-19115.3 daysTechnetium-99m6.02 hours