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': 'Pentameric antibody is: \nSelect and explain. \nA. IgD, B. IgG, C. IgM, D. IgA', 'role': 'user'}, {'content': 'Answer: C \nExplanation: IgM', 'role': 'assistant'}]