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 most common organism which can contaminate crowded army camps is ? 
Select and explain. 
A. Klebsiella, B. E. coli, C. Neisseria meningitidis, D. Staphylococcus
C: Neisseria meningitidis
Answer: C: Neisseria meningitidis 
Explanation: Epidemics of Neisseria meningitidis usually occur in closed crowded conditions like jails or army camps.