This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Bacteria, Subject name: Microbiology
[{'content': 'Gravis, Intermedius and Mitis are biotypes of: \nSelect and explain. \nA. Clostridium perfringens, B. Corynebacterium diphtheria, C. Capnocytophaga, D. Klebsiella', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Ans. B. Corynebacterium diphtheriaGravis, Intermedius, Mitis and Belfanti are biotypes of Corynebacterium diphtheria. Gravis causes most severe disease.', 'role': 'assistant'}]