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: Medicine
[{'content': 'Locate the renal stone with pain radiating to medial side of thigh and perineum due to slipping of stone in males: \nSelect and explain. \nA. At pelvic brim, B. Intramural opening of ureter, C. Junction of ureter and renal pelvis, D. At crossing of gonadal vessels and ureter', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Answer is A (At pelvic brim): Pain radiating to medial side of thitth and perineum suggetsts a stone in lower poion of ureter (proximal to orifice) or at pelvic brim.', 'role': 'assistant'}]