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': 'True about corynebacterium diphtheriae: \nSelect and explain. \nA. All types produce toxin, B. Toxin production is dependent upon critical concentration of iron, C. Heat stable toxin, D. Inhibit cAMP', 'role': 'user'}, {'content': "Answer: B \nExplanation: Ans. is. 'b' i. e. Toxin production is dependent upon critical concentration of iron", 'role': 'assistant'}]