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: Surgery
[{'content': '30 years old lady presented with acute pain abdomen, constipation and vomiting suspecting acute intestinal obstruction. The investigation of choice for the patient is - \nSelect and explain. \nA. Ba enema, B. X-ray abdomen erect posture, C. USG, D. CT scan', 'role': 'user'}, {'content': "Answer: B \nExplanation: Ans. is 'b' i.e. X-ray abdomen erect posture", 'role': 'assistant'}]