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: Gynaecology & Obstetrics
[{'content': 'Causes of Hydramnios are all except : \nSelect and explain. \nA. Anencephaly, B. Oesophageal atresia, C. Posterior urethral value, D. Twins', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Posterior urethral value', 'role': 'assistant'}]