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': 'Posterior urethral valve are commonly observed in - \nSelect and explain. \nA. Boys, B. Girls, C. Adult males, D. Adult females', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]