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: Medicine
[{'content': "Farmer's lung is caused by exposure to - \nSelect and explain. \nA. Cryptostroma corticale, B. Asperigullus, C. Thermophilic actinomycetes, D. Grain dust", 'role': 'user'}, {'content': 'Answer: C \nExplanation: None', 'role': 'assistant'}]