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: Social & Preventive Medicine
Presence of it indicates remote contamination of water 
Select and explain. 
A. Streptococci, B. Staphalococci, C. Clastridium pertringes, D. Nibrio
C: Clastridium pertringes
Answer: C: Clastridium pertringes 
Explanation: None