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
In a Down's syndrome patient posted for surgery, the necessary preoperative investigation to be done is – 
Select and explain. 
A. CT Brain, B. Echocardiography, C. Ultrasound Abdomen, D. X-ray cervical spine
B: Echocardiography
Answer: B: Echocardiography 
Explanation: Congenital heart disease (especially endocardial cushion defect) is frequently found in Down's syndrome. Echocardiography is therefore considered necessary preoperative investigation.