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 diphtheria includes all of the following except: \nSelect and explain. \nA. 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", 'role': 'user'}, {'content': 'Answer: D \nExplanation: Ans. (d) Toxigenicity is mediated by chromosomal change "Corynebacteriophage beta carries the structural gene (tox+) encoding diphtheria toxin and a family of closely related corynebacteriophage are responsible for toxigenic conversion of tox- C.diphtheria to tox+ phenotype." Elek\'s gel precipitation test is in vitro test for toxin detection.', 'role': 'assistant'}]