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': 'Vaginal delivery is impossible in : \nSelect and explain. \nA. Persistent Mento-posterior presentation, B. Persistent occipito-posterior presentation, C. Mento-anterior presentation, D. Breech presentation', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Persistent Mento-posterior presentation', 'role': 'assistant'}]