This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Radiotherapy Pa 1, Subject name: Radiology
Half life of cobalt-60 is - 
Select and explain. 
A. 74.5 years, B. 5.2 years, C. 30 years, D. 2.6 years
B: 5.2 years
Answer: B: 5.2 years 
Explanation: Impoant Radioisotopes Half Life RADIOISOTOPE HALF LIFE IODINE 131 8 DAYS IODINE 125 60 DAYS IODINE 124 4 DAYS IODINE 123 13 HOURS PHOSPHORUS -32 14 DAYS RADIUM (RA-226) 1622 years Cobalt -60 5.2 years Cesium - 137 30 years TC- 99m 6 hours Iridium (Ir-192) 74.5 Days 18F (18FDG) 110 min Strontium 89 50.5 days