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
Radio isotope used in both Teletherapy and brachy therapy 
Select and explain. 
A. Radium-226, B. Gold-198, C. Cesium-137, D. Iodine-125
C: Cesium-137
Answer: C: Cesium-137 
Explanation: Co-60 and Cs-137 are used in both Teletherapy and brachytherapy.