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': 'Longest fetal diameter: \nSelect and explain. \nA. Biparietal, B. Suboccip tobregmatic, C. Occipitofrontal, D. Mentovertical', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Ans is d, i.e. MentoverticalFetal diameters-AP diameters are always longer than Transverse diameter of fetal head.Longest diameter is-Mentovertical diameter (14 cms) followed by submentovertical diameter.', 'role': 'assistant'}]