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: Microbiology
Farmer's lung is caused by - 
Select and explain. 
A. Micromonospora faeni, B. Aspergillosis, C. Histoplasma capsulatum, D. All of the above
A: Micromonospora faeni
Answer: A: Micromonospora faeni 
Explanation: None