This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: G.I.T, Subject name: Pharmacology
[{'content': 'Which stone is common in chronic laxative use: \nSelect and explain. \nA. Xanthine, B. Cysteine, C. Ammonia urate, D. Struvite', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Ans. c. Ammonia urateRef: Campbells Urology/P. 210Chronic laxative use leads to decreased sodium in the urine, as most sodium is excreted by GIT.Hence urate binds more with ammonia and this leads to ammonia urate stones.', 'role': 'assistant'}]