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': 'Shoulder pain post laparoscopy is due to: \nSelect and explain. \nA. Subphrenic abscess, B. CO2 retention, C. Positioning of the patient, D. Compression of the lung', 'role': 'user'}, {'content': 'Answer: B \nExplanation: CO2 retention [Ref: J Shoulder pain is although a minor complication is exceedingly common and is due to the presence of a significant amount of residual carbon dioxide in the peritoneal cavity, trapped under the diaphragm and causing irritation of the diaphragm and thus referred pain to the shoulder through the phrenic nerve.', 'role': 'assistant'}]