This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Occupational Health, Subject name: Social & Preventive Medicine
[{'content': 'Of 25 persons are working on a project for 30 years. There is how many person-years of employement. \nSelect and explain. \nA. 75, B. 750, C. 120, D. 1200', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Ans. is \'b\' i.e., 750 "10000 people working for 1 year would lead to 1000 person years of employment"* Thus, 25 persons working for 30 years will lead to 750 person-years of employment.', 'role': 'assistant'}]