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" colitis is caused by: 
Select and explain. 
A. Clostridium botulinum spores, B. Clostridium difficile, C. Clostridium perfringens, D. Clostridium tetani
B: Clostridium difficile
Answer: B: Clostridium difficile 
Explanation: Clostridium difficile