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': "Which of the following is the commonest cause of farmer's lung? \nSelect and explain. \nA. Micropolyspora faeni, B. Thermoactinomyces sacchari, C. Mycobacterium bovis, D. None of the above", 'role': 'user'}, {'content': "Answer: A \nExplanation: Farmer's lung is caused due to inhalation of mouldy hay or grain. Thermophillic actinomyeces, commonly Micropolyspora faeni is the common cause of farmer's lung. Ref: Park 21st edition, page 748. Chapter: Occupational health.", 'role': 'assistant'}]