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: Pharmacology
[{'content': 'All the drugs given below can be used to protect gastric ulcer except \nSelect and explain. \nA. Colloidal bismuth salt, B. Magnesium hydroxide, C. Misoprostal, D. Sucralfate', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]