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: Social & Preventive Medicine
[{'content': 'Diphtheria carrier are diagnosed by \nSelect and explain. \nA. Gram’s staining, B. Throat culture, C. Albert’s staining, D. Schick test', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]