This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Immunology, Subject name: Microbiology
[{'content': 'Precipitation & agglutination are caused by: \nSelect and explain. \nA. IgG and IgM, B. IgM and IgG, C. IgM and IgA, D. IgD and IgA', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Ans. A. IgG and IgMPrecipitation occurs with IgG when the antigen is soluble while agglutination occurs with IgM when the antigen is particulate/insoluble', 'role': 'assistant'}]