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
Which is used in teletheraphy & Brachytherapy both – 
Select and explain. 
A. Iridium 127, B. Cobalt 60, C. Pallidium, D. Iodine 131
B: Cobalt 60
Answer: B: Cobalt 60 
Explanation: Co - 60 and Cs - 137 are used both in teletherapy and brachytherapy