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 type of atrial septal defect is ? 
Select and explain. 
A. Ostium primum, B. Ostium secondum, C. Endocardial cushion defect, D. Endocardial hyperophy
B: Ostium secondum
Answer: B: Ostium secondum 
Explanation: Ans. is 'b' i.e., Ostium secondum