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': 'Investigation of choice for diphtheria carrier is: \nSelect and explain. \nA. Throat swab culture, B. Gram’s stain, C. Albert’s stain, D. Ziehl Neelsen stain', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Carriers can be detected only by cultural method.\nSwab should be taken from both the nose and throat.', 'role': 'assistant'}]