This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: GIT 1, Subject name: Anatomy
[{'content': 'The narrowest pa of the ureter is at: \nSelect and explain. \nA. Uretero-pelvic junction, B. Iliac vessel crossing, C. Pelvic ureter, D. Ureterovesicle junction', 'role': 'user'}, {'content': 'Answer: D \nExplanation: The narrowest lumen is where the ureter enters the bladder wall (ureterovesicle junction) and may be responsible for arresting the passage of stones of as little as 2-3 mm. Note: Sometime the question may not have the option of ureterovesical junction, in that case the intramural ureter (the pa inside detrusor) may be taken as the answer.', 'role': 'assistant'}]