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: Medicine
TRUE about immunoglobulins is: 
Select and explain. 
A. IgE fixes complements, B. IgM fixes complements, C. IgG is found in minimum concentration, D. IgG is elevated in primary immune response
B: IgM fixes complements
Answer: B: IgM fixes complements 
Explanation: Answer is B (IgM fixes complements): IgM and IgG .fix complement the classical pathway