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: Dental
[{'content': 'What is PULP cap? \nSelect and explain. \nA. Capping of the exposed vital pulp with a thin layer of inert lining or base material, B. Capping of exposed vital pulp tissue by placing a layer of mineral trioxide aggregate (MTA) or calcium hydroxide, C. A method of isolation used during root canal treatment, D. An early stage of tooth development', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]