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': 'Gas gangrene is caused by: March 2012 \nSelect and explain. \nA. Clostridium welchii, B. Clostridium tetani, C. Clostridium botulinum, D. Clostridium difficile', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Ans: A i.e. Clostridium welchii Conditions and pathogens Established pathogens (clostridium) for gas gangrene (group) includes Cl. Perfringens/ welchii, Cl. septicum & Cl. Novyi Established pathogen (clostridium) for tetnaus include Cl. Tetani Established pathogens (clostridium) for food poisoning (group) includes Cl. Perfringens type A (gastroenteritis), Cl. Perfringens type C (necrotising enteritis) and Cl. Botulinum (botulism) Established pathogens (clostridium) for acute colitis include Cl. difficile', 'role': 'assistant'}]