This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Placenta Previa, Subject name: Gynaecology & Obstetrics
[{'content': 'The best way to diagonse the degree of placenta previa is- \nSelect and explain. \nA. Transvaginal sonography, B. Double set-up examination, C. Observation during C.S., D. Examination of placenta after delivery', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Previa can be confirmed with an ultrasound. Transvaginal ultrasound has superior accuracy as compared to transabdominal one, thus allowing measurement of distance between placenta and cervical os', 'role': 'assistant'}]