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': 'Diphtheria is pathogenic only when infected with \nSelect and explain. \nA. Beta phage, B. Alfa phage, C. Lambda k12, D. Delta phage', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]