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: Unknown
[{'content': 'Smallest cross-section of large bowel is seen at: \nSelect and explain. \nA. Descending colon, B. Ascending colon, C. Transverse colon, D. Sigmoid colon', 'role': 'user'}, {'content': 'Answer: D \nExplanation: (Refer: Richard S. Snell’s Clinical Anatomy by Regions, 9th edition, pg no: 158)\nCharacteristic Features of Rectosigmoid Junction\n\nThe diameter of the large intestine narrows.\nThere is an absence of complete peritoneal investment.\nThere is no true mesentery.\nThe three taeniae coli diverge to form a continuous longitudinal muscle coat on the rectum.\nThere are no appendices epiploicae.\nEndoscopically, an acute angle is encountered at the narrowing of the rectosigmoid and the rectal mucosa is smooth and flat, whereas the mucosa of the sigmoid forms prominent rugal folds.', 'role': 'assistant'}]