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
The most common causative organism for Traveller's diarrhoea is - 
Select and explain. 
A. E. coli, B. Shigella, C. Norwalk virus, D. Rotavirus
A: E. coli
Answer: A: E. coli 
Explanation: None