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': "Cause of Farmer's lung - \nSelect and explain. \nA. Cotton dust, B. Grain dust, C. Sugarcane dust, D. Iron", 'role': 'user'}, {'content': "Answer: B \nExplanation: Ans. is 'b' i.e., Grain dust Farmer's lung is caused by Hay or grain dust", 'role': 'assistant'}]