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': 'The element used for intracavitary in carcinoma cervix: \nSelect and explain. \nA. Caesium, B. Cobalt-60, C. Strontium, D. Radio iodine', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Ans. Caesium', 'role': 'assistant'}]