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': 'Least sensitive structure to radiation is: \nSelect and explain. \nA. Uterus, B. Cervix, C. GIT, D. Vagina', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Ans. Vagina', 'role': 'assistant'}]