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
Gravis, Intermedius and Mitis are biotypes of: 
Select and explain. 
A. Clostridium perfringens, B. Corynebacterium diphtheria, C. Capnocytophaga, D. Klebsiella
B: Corynebacterium diphtheria
Answer: B: Corynebacterium diphtheria 
Explanation: Ans. B. Corynebacterium diphtheriaGravis, Intermedius, Mitis and Belfanti are biotypes of Corynebacterium diphtheria. Gravis causes most severe disease.