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': 'Element most commonly used in brachytherapy of carcinoma cervix: March 2005 \nSelect and explain. \nA. Carbon, B. Technetium, C. Nitrogen, D. Cesium', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Ans. D: Cesium', 'role': 'assistant'}]