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: Unknown
[{'content': 'Presentation, when the engaging diameter is Mentovertical, is? \nSelect and explain. \nA. Brow, B. Face, C. Vertex, D. Breech', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Ans-ARef.: Dutta 6th edp-393', 'role': 'assistant'}]