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: Surgery
[{'content': 'One of the following is characterised by RIM sign - \nSelect and explain. \nA. Hydronephrosis (Gross), B. Hypernephroma, C. Chronic pyelonephritis, D. Polycystic kidney', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]