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
Preformed enterotoxins are formed by ? 
Select and explain. 
A. Clostridium tetani, B. E.coli, C. Shigella sonnei, D. Clostridium perfringens
D: Clostridium perfringens
Answer: D: Clostridium perfringens 
Explanation: None