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': 'Which is best material for RPD impression \nSelect and explain. \nA. Impression plaster, B. Irreversible hydrocolloid, C. Reversible hydrocolloid, D. None of the above', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]