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
[{'content': 'Most common organism responsible for pseudo membranous colitis is ? \nSelect and explain. \nA. Clostridium difficile, B. Clostridium botulism, C. Clostridium histolyticum, D. Clostridium butyricum', 'role': 'user'}, {'content': "Answer: A \nExplanation: Ans. is 'a' i.e., Clostridium difficile", 'role': 'assistant'}]