This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Stomach & Duodenum, Subject name: Surgery
[{'content': 'In congenital pyloric stenosis the defect usually lies in the antral: \nSelect and explain. \nA. Nerve fibers, B. Circular muscle fibers, C. Longitudinal muscle fibers, D. Mucosa', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Ans. (b) Circular muscle fibersRef: Bailey and Love 26th Edition, Page 113* Circular muscle hypertrophy results- hence pyloromyotomy we cut these muscles', 'role': 'assistant'}]