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': 'The engaging diameter in deflexed head is: \nSelect and explain. \nA. Biparietal dirnaeter, B. Occipitofrontal diameter, C. Suboccipito bregamatic diameter, D. Bitemporal diameter', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Occipitofrontal diameter', 'role': 'assistant'}]