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': 'Commonest cause of enlarged cardiac shadow in X–ray of a child is – \nSelect and explain. \nA. PDA, B. Coarctation of Aorta, C. Pericarditis, D. Rheumatic carditis', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Cardiac failure causes cardiomegaly\nMC cause of cardiac failure in children (elder than infants) is rheumatic fever and rheumatic heart disease.', 'role': 'assistant'}]