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': 'Shoest diameter is : \nSelect and explain. \nA. Diagonal conjugate, B. Obstetric conjugate, C. True conjugate, D. All are equal', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Obstetric conjugate', 'role': 'assistant'}]