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
TRUE about immunoglobulins is - 
Select and explain. 
A. IgE fixes complement, B. IgM fixes complement, C. IgG is found in minimum concentration, D. IgG is elevated in primary immune response
B: IgM fixes complement
Answer: B: IgM fixes complement 
Explanation: IgM is paicularly effective at complement activation by binding to C1 Ref: Ananthanarayan & Parker's textbook of microbiology 9th edition pf:98