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': 'Steinstrasse is - \nSelect and explain. \nA. Staining of stones, B. Stones because of stress, C. Failure of ESWL, D. Ureteric obstruction due to fragments in ureter', 'role': 'user'}, {'content': "Answer: D \nExplanation: Ans. is 'd' i.e., Ureteric obstruction due to fragments in ureter", 'role': 'assistant'}]