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': 'Safety officer is appointed in factories when no of  workers are \nSelect and explain. \nA. > 500, B. > 1000, C. > 1500, D. > 2000', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]