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: Social & Preventive Medicine
[{'content': 'Best way to prevent Nosocomial infection \nSelect and explain. \nA. Wearing mask, B. Hand washing, C. Maintaining distance, D. Frequent Bathing', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]