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 28 year old male presents with high fever, and signs suggestive of meningitis. On CSF microscopy, a gram-positive bacilli is seen. Organism is 
Select and explain. 
A. S.pneumoniae, B. H.influenzae, C. Listeria, D. Mycoplasma
C: Listeria
Answer: C: Listeria 
Explanation: Among the options only gram positve bacilli is Listeria.