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 the function of humectants in dentrifrices: \nSelect and explain. \nA. Liquefies the dentrifrice, B. Prevents water loss and hardening on exposure to air, C. Flavors the tooth paste, D. Cleans tooth surface effectively', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]