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 best way to diagnose the degree of placenta pre is \nSelect and explain. \nA. Trans vaginal sonography, B. Double set-up examination, C. Observation during C.S., D. Examination of placenta after delivery', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Trans vaginal sonography', 'role': 'assistant'}]