This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Anitibody, Subject name: Microbiology
The Fc piece of which immunoglobulin fixes complement 1 - 
Select and explain. 
A. IgA, B. IgG, C. IgM, D. IgE
C: IgM
Answer: C: IgM 
Explanation: Ans. is 'c' > 'b' i.e., IgM > IgG o Make it very clear in your mind that both IgM and IgG fix C1." CH2 of IgG and CH4 of IgM bind to C1q portion of C1"-------Ananthanarayan" Clq portion of Cl is an aggregate of 18 polypeptides that binds to the Fc portion of IgM and IgG"--LANGE microbiologyo However, if you will have to choose one option, IgM is the best because IgM is more effective than IgG for complement fixation.