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
Which of the following is the necessary pre-operative investigation which has to be done in a patient with Down's syndrome posted for surgery? 
Select and explain. 
A. CT Brain, B. Echocardiography, C. Ultrasound Abdomen, D. X-Ray cervical spine
B: Echocardiography
Answer: B: Echocardiography 
Explanation: Down's syndrome is associated with cardiac manifestations such as Endocardial cushion defect, ASD, VSD and Tetrology of fallot. So echocardiography is the necessary pre-operative investigation to be done before surgery in a patient with Downs' syndrome. Ref: Harrison's Principles of Internal Medicine, 16th Edition, Page 1382