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: Medicine
A young female presents with history of dyspnoea on exertion. On examination, she has wide, fixed split S2 with ejection systolic murmur (III/VI) in left second intercostal space. Her EKG shows left axis deviation. The most probable diagnosis is 
Select and explain. 
A. Total anomalous pulmonary venous drainge, B. Tricuspid atresia, C. Ostium primum atrial septal defect., D. Ventricular septal defect with pulmonary arterial hypertension
C: Ostium primum atrial septal defect.
Answer: C: Ostium primum atrial septal defect. 
Explanation: None