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': 'The commonest site of perforation during colonoscopy is - \nSelect and explain. \nA. Caecum, B. Hepatic flexure, C. Splenic flexure, D. Sigmoid colon', 'role': 'user'}, {'content': 'Answer: D \nExplanation: • Risks of colonoscopy: Perforation and hemorrhage\n• MC site of bleeding after colonoscopy: Stalk after polypectomy.\n• MC site of perforation during colonoscopy: Sigmoid colon\n• Perforation can be caused by excessive air pressure, tearing of the antimesenteric border of the colon from excessive pressure on colonic loops, and at the sites of electrosurgical applications', 'role': 'assistant'}]