This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Gastrointestinal tract, Subject name: Pharmacology
[{'content': 'All the following are bulk-forming laxatives except \nSelect and explain. \nA. Polycarbophil, B. Psyllium, C. Methylcellulose, D. Glycerin', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Glycerin is a hyperosmotic laxative.Bulk formers: Polycarbophil, psyllium, and methylcellulose preparations. the dosage varies, consult product labeling.Hyperosmotics: Glycerin, 2-3 g suppository per rectum daily. Polyethylene glycol 3350 (powder), 17 g dissolved in 4-8 oz of beverage dailyStool softeners: Docusate sodium, 50-500 mg daily. Docusate calcium, 240 mg dailyStimulant laxatives: Bisacodyl, 5-15 mg daily. Senna, the dosage varies, consult product labelingRef: Katzung 13th ed. Pg 1090', 'role': 'assistant'}]