This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Environment and health, Subject name: Social & Preventive Medicine
[{'content': 'The maximum permissible level of occupational exposure to radiation is ..... Per year - \nSelect and explain. \nA. 5 rad, B. 2 rad, C. 10 rad, D. 50 rad', 'role': 'user'}, {'content': "Answer: A \nExplanation: Park's textbook of preventive and social medicine 23rd edition. * The amount of radiation from outer space and background radiationhas been estimated to be 0.1 rad a year,the additional permissible dose from man made sources should not exceed 5 rad a year.", 'role': 'assistant'}]