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': "Bacteriophage was discovered by: \nSelect and explain. \nA. Robert Koch, B. Twort and d'herelle, C. Menkin, D. Metchinkoff", 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]