<prompt> The best way to diagonse the degree of placenta previa is-Transvaginal sonographyDouble set-up examinationObservation during C.S.Examination of placenta after delivery  <response>: 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 