A 28 year old G2P1 woman with a history of a prior cesarean delivery presents at 36weeks gestation with a complaints of vaginal bleeding. she notes no contractions, but awoke this morning with vaginal bleeding equivalent to heavy menstrual flow. you obtain an ultrasound as part of her workup for third trimester bleeding. ultrasound is the primary diagnostic tool which cause of third trimester bleeding?

a) uterine rupture
b) placental abruption
c) placenta previa 
d) vaginal laceration

The correct answer - C