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': 'Best investigation for air in peritoneal cavity is - \nSelect and explain. \nA. USG, B. Laparotomy, C. Laparoscopy, D. X-ray abdomen-erect view', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Not given in the option but free gas under the diaphragm is best shown on an erect chest x-ray. If the patient is too ill for an erect film, a lateral decubitus film is done.', 'role': 'assistant'}]