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
The commonest site of perforation during colonoscopy is - 
Select and explain. 
A. Caecum, B. Hepatic flexure, C. Splenic flexure, D. Sigmoid colon
D: Sigmoid colon
Answer: D: Sigmoid colon 
Explanation: • Risks of colonoscopy: Perforation and hemorrhage
• MC site of bleeding after colonoscopy: Stalk after polypectomy.
• MC site of perforation during colonoscopy: Sigmoid colon
• 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