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': "In a Down's syndrome patient posted for surgery, the necessary preoperative investigation to be done is – \nSelect and explain. \nA. CT Brain, B. Echocardiography, C. Ultrasound Abdomen, D. X-ray cervical spine", 'role': 'user'}, {'content': "Answer: B \nExplanation: Congenital heart disease (especially endocardial cushion defect) is frequently found in Down's syndrome. Echocardiography is therefore considered necessary preoperative investigation.", 'role': 'assistant'}]