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
[{'content': 'Which is going to best declare the case as that of interatrial septal defect with other cardiac abnormalities – \nSelect and explain. \nA. Elevated pressurein left atrium, B. Elevated pressure in right atrium, C. Elevated PO2 in pulmonary artery, D. Systolic murmur', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]