This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: General anatomy, Subject name: Anatomy
[{'content': 'Which of the following immunoglobulin does not fix complement \nSelect and explain. \nA. IgA, B. IgG, C. IgM, D. IgE', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Ref Robbins immuno system chapter ... immunoglobulin topic ; see tables for details complement-fixing antibody antibody (primarily IgM and the IgG subclasses 1, 2, and 3) that activates complement when reacted with antigen. ... In humans this antibody, also known as reagin, is of the immunoglobulin class known as IgE.', 'role': 'assistant'}]