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: Medicine
Most common causative organism for ascending cholangitis is - 
Select and explain. 
A. Streptococcus, B. Proteus, C. E. coli, D. Anaerobes
C: E. coli
Answer: C: E. coli 
Explanation: None