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
Animal reservoir for swine influenza virus is 
Select and explain. 
A. Field mice, B. Urban rats, C. Pigs, D. Calomys callosus
C: Pigs
Answer: C: Pigs 
Explanation: The swine flu virus H1N1 caused a localised outbreak in a militiary camp in USA.