This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: General obstetrics, Subject name: Anatomy
[{'content': 'Engagement of fetal head is with reference to \nSelect and explain. \nA. Biparietal diameter, B. Bitemporal diameter, C. Occipitofrontal diameter, D. Suboccipitofrontal diameter', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Engagement is said to occur when the largest transverse diameter of fetal head crosses the pelvic inlet. Largest transverse diameter of fetal head is biparietal diameter', 'role': 'assistant'}]