This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Fetal Skull and Maternal Pelvis, Subject name: Gynaecology & Obstetrics
[{'content': 'In a vertex presentation the diameter of engagement is: \nSelect and explain. \nA. Suboccipitobregmatic, B. Suboccipito-frontal, C. Occipitofrontal, D. Bitemporal', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Ans. A. SuboccipitobregmaticFetal skulla. Mento vertical diameter =14.5cm,b. Submentovertical =11.5cm,c. Sub occipitofrontal =10cm,d. Suboccipitobregmatic =9.5cm (diameter of engagement in vertex presentation),e. Biparietal =9.5cm.', 'role': 'assistant'}]