This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: C.V.S., Subject name: Pediatrics
[{'content': 'A young female presents with history of dyspnea on exertion. On examination, she has wide, fixed split S2 with ejection systolic murmur (III/VI) in left second intercostal space. Her ECG shows left axis deviation. The most probable diagnosis is: \nSelect and explain. \nA. Total anomalous pulmonary venous drainage, B. Tricuspid atresia, C. Ostium primum atrial septal defect, D. Ventricular septal defect with pulmonary arterial hypertension', 'role': 'user'}, {'content': "Answer: C \nExplanation: c. Ostium primum atrial septal defect(Ref: Nelson's 20/e p 2189, Ghai 8/e p 413)Wide fixed splitting of S2 in association with ejection systolic murmur suggests the diagnosis of atrial septal defectThe presence of left axis deviation in A.S.D., suggests ostium primum type of defect.", 'role': 'assistant'}]