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 organism causing "Pseudomembranous" colitis: 
Select and explain. 
A. The organism causing "Pseudomembranous" colitis:, B. Clostridium perfringens, C. Clostridium tetani, D. Clostridium botulinum
A: The organism causing "Pseudomembranous" colitis:
Answer: A: The organism causing "Pseudomembranous" colitis: 
Explanation: Clostridium difficile