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
True about corynebacterium diphtheriae: 
Select and explain. 
A. All types produce toxin, B. Toxin production is dependent upon critical concentration of iron, C. Heat stable toxin, D. Inhibit cAMP
B: Toxin production is dependent upon critical concentration of iron
Answer: B: Toxin production is dependent upon critical concentration of iron 
Explanation: Ans. is. 'b' i. e. Toxin production is dependent upon critical concentration of iron