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': 'Investigation of choice for CHPS \nSelect and explain. \nA. USG, B. x-ray, C. CT, D. MRI', 'role': 'user'}, {'content': "Answer: A \nExplanation: Ans. (a) USGRef: Bailey and Love page 113-114/26th edition* IOC for Congenital Hypertrophic Pyloric stenosis - USG* Palpated as a Olive tumor in right Upper quadrant.* If the history and clinical mass is there - no need of USG - directly we can do Ramstedt's pylromyotomy", 'role': 'assistant'}]