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: Pediatrics
[{'content': 'Balloon valvotomy is successful in all of the following cases except – \nSelect and explain. \nA. Congenital pulmonary stenosis, B. Calcified mitral stenosis, C. Mitral stenosis is pregnancy, D. Congenital aortic stenosis', 'role': 'user'}, {'content': 'Answer: B \nExplanation: It is indicated in MS without calcification.', 'role': 'assistant'}]