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': 'ElekS Gel test is used in:( \nSelect and explain. \nA. Influenza, B. Diphtheria, C. Brucellosis, D. Cholera', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Diphtheria', 'role': 'assistant'}]