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
The best way to diagonse the degree of placenta previa is- 
Select and explain. 
A. Transvaginal sonography, B. Double set-up examination, C. Observation during C.S., D. Examination of placenta after delivery
A: Transvaginal sonography
Answer: A: Transvaginal sonography 
Explanation: 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