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': "All of the following may occur in Down's syndrome, except: \nSelect and explain. \nA. Hypothyroidism, B. Undescended testis, C. Ventricular septal defect, D. Brushfield's spots", 'role': 'user'}, {'content': "Answer: B \nExplanation: Undescended testis has not been described as an association with Down's syndrome. Hypothyroidism, ventricular septal defect, Brushfield's spots are seen in Down's syndrome. Ref: Essential Pediatrics By O P Ghai, 6th Edition, Page 592; Down Syndrome By Mark Selikowitz, 2008, Preview.", 'role': 'assistant'}]