This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Abdomen and pelvis, Subject name: Anatomy
[{'content': 'Ureteric constriction is seen at all the following positions, except \nSelect and explain. \nA. Ureteropelvic junction, B. Ureterovesical junction, C. Crossing of iliac aery, D. Ischial spine', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Ureter has three constrictions, which are the most common sites of renal calculus obstruction: at the pelvi-ureteric junction (PUJ) of the renal pelvis and the ureter as the ureter enters the pelvis and crosses over the common iliac aery bifurcation at the vesicoureteric junction (VUJ) as the ureter obliquely enters the bladder wall Ref - BDC vol2 6e , researchgate.net', 'role': 'assistant'}]