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 of the following causes melanosis coli? \nSelect and explain. \nA. Senna, B. Sorbitol, C. Magnesium Sulphate, D. Bisacodyl', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Ans. A. SennaMelanosis coli is a disorder of pigmentation of the wall of the colon, often identified at the time of colonoscopy. It is benign, and may have no significant correlation with disease. The brown pigment is lipofuscin in macrophages, not melanin.The most common cause of melanosis coli is the extended use of laxatives, and commonly anthraquinone containing laxatives such as senna, aloe vera and other plant glycosides', 'role': 'assistant'}]