This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Systemic Bacteriology (Gram Positive Bacilli, Gram Negative Bacilli), Subject name: Microbiology
[{'content': 'Which is the most common causative agent of gas gangrene? \nSelect and explain. \nA. Cl. histolyticum, B. Cl. novyi, C. Cl. septicum, D. Cl. perfringens', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Clostridium perfringens is the most common causative agent of gas gangrene. Gas gangrene: Established agents: C. perfringens (Most Common, 60-80%) and C. novyi and C. septicum (20-40%). Probable agents: C. histolyticum, C. sporogenes, C. fallax, C. bifermentans, C. sordellii, C. aerofoetidum and C. teium.', 'role': 'assistant'}]