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: Radiology
[{'content': "Preoperative investigation to be done in down's syndrome posted for surgery \nSelect and explain. \nA. CT, B. MRI, C. X-ray of hand, D. Echo", 'role': 'user'}, {'content': "Answer: D \nExplanation: Endocardial cushion defect is most commonly present in Down's syndrome patient.\nEcho is done prior.", 'role': 'assistant'}]