This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Abdominal Injury, Subject name: Surgery
[{'content': 'A case of polytrauma with blunt abdominal injury presents to the casualty. The first investigation to evaluate his abdomen is - \nSelect and explain. \nA. USG, B. CT Scan, C. CompleteHemogram, D. Abdominal X-ray', 'role': 'user'}, {'content': "Answer: A \nExplanation: Ans. is 'a' i.e., USG o Has been explained in previous sessions", 'role': 'assistant'}]