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': 'In Teletherapy setup all are used except \nSelect and explain. \nA. Irridium-191, B. Co - 60, C. Simulator, D. Computer', 'role': 'user'}, {'content': 'Answer: A \nExplanation: A i.e. Irridium 191', 'role': 'assistant'}]