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: Unknown
In Corynebacterium diphtheria 
Select and explain. 
A. Deep invasion is not seen, B. Elek’s test is done for toxigenicity, C. Metachromatic granules are seen, D. Toxigenicity is mediated by chromosomal change
D: Toxigenicity is mediated by chromosomal change
Answer: D: Toxigenicity is mediated by chromosomal change 
Explanation: • Diphtheria acts by its toxin and invasion is not seen.
• Elekc gel precipitation test is done for determination of pathogenicity of diphtheria.
• Metachromatic granules are seen also called as Babes earnest granules. Bacteriophages (extra-chromosomal) are responsible for toxigenicity by phage conversion.