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
A patient is suffering from pneumonia. Laboratory study shows acid-fast filamentous bacterium. The causative organism is ? 
Select and explain. 
A. M. tuberculosis, B. Actinomyces, C. Nocardia, D. Mycobacterium Avium intracellulare
C: Nocardia
Answer: C: Nocardia 
Explanation: Ans. is 'c' i.e., Nocardia Symptoms of pneumonia by a filamentous acid fast bacterium suggest the diagnosis of Nocardia.