This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Bacteriology, Subject name: Microbiology
[{'content': 'True about diphtheria is \nSelect and explain. \nA. Capsulated bacteria causes infection, B. Ratio of carriers and clinical cases is one, C. Gram positive and motile, D. Lysogenic phase causes disease', 'role': 'user'}, {'content': "Answer: D \nExplanation: The toxigenicity of the diphtheria bacillus depends on the presence of corynephages(tox+) in it which acts as the genetic determinant controlling toxin production. Non-toxigenic strains may be rendered toxigenic by infecting them with the beta or some other phage. This is known as lysogenic or phage conversion. The toxigenicity remains only as long as the bacillus is lysogenic. When the bacillus is cured of its phage, as by growing it in the presence of antiphase serum, it loses its toxigenic capacity. Reference: Textbook of Microbiology; Anathanarayan and panicker's; 10th edition; Page no: 240", 'role': 'assistant'}]