This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Systemic Bacteriology (Gram Positive Bacilli, Gram Negative Bacilli), Subject name: Microbiology
There is an outbreak of watery diarrhea due to Shigella occurred in several day care centers in Pondicherry. Which Shigella sp. is most likely involved? 
Select and explain. 
A. S. boydii, B. S. flexneri, C. S. sonnei, D. S. dysenteriae
B: S. flexneri
Answer: B: S. flexneri 
Explanation: S. flexneri- most common in India- Shigella sonnei is the most common in developed countries and generally causes a watery diarrhea.- Shigella dysenteriae causes dysentery characterized by tenesmus and the production of scanty, bloody stools.