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
[{'content': 'Radio isotope used in both Teletherapy and brachy therapy \nSelect and explain. \nA. Radium-226, B. Gold-198, C. Cesium-137, D. Iodine-125', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Co-60 and Cs-137 are used in both Teletherapy and brachytherapy.', 'role': 'assistant'}]