This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Pediatrics
Most common ASD is ? 
Select and explain. 
A. Ostium primum, B. Patent foramen ovale, C. Ostium secondum, D. Sinus venosus
C: Ostium secondum
Answer: C: Ostium secondum 
Explanation: 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