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': 'First immunoglobin to appear following infection: \nSelect and explain. \nA. IgG, B. IgM, C. IgA, D. IgE', 'role': 'user'}, {'content': 'Answer: B \nExplanation: IgM', 'role': 'assistant'}]