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: Surgery
Acute mesenteric lymphadenitis is caused by? 
Select and explain. 
A. E. Coli, B. Alpha Hemolytic streptococci, C. Hemophilus influenza, D. Yersinia
D: Yersinia
Answer: D: Yersinia 
Explanation: Acute mesenteric lymphadenitis is the diagnosis usually given when enlarged, slightly reddened lymph nodes are encountered at the root of mesentery along with normal appendix, when a patient suspected of appendicitis is opened up. Whether this is a single, discrete entity is unclear, since the causative factor is not known. Some of these patients have infection with Y. pseudotuberculosis or Y. enterocolitica, in which case the diagnosis can be established by culture of the mesenteric nodes by serological titres. Children seem to be affected more frequently than men. Ref: Harrison 17/e, Page 1916