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
Pseudomembranous enterocolitis is caused by: 
Select and explain. 
A. Cl. perfringens, B. Cl. welchii, C. Cl. difficile, D. Pseudomonas
C: Cl. difficile
Answer: C: Cl. difficile 
Explanation: Cl. difficile