<prompt> Most common ASD is ?Ostium primumPatent foramen ovaleOstium secondumSinus venosus  <response>: Ans. is c i.e., Osteum secondum ASD can occur in any poion of atrial septum - Secundum Primum Sinus venosus Absent atrial septum leads to single atrium Ostium secondum defect Defect in region of fossa ovalis Most common form of ASD 