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: Microbiology
Complement binding immunoglobin via the classical pathway is 
Select and explain. 
A. IgG & IgM, B. IgG & IgA, C. IgG & IgD, D. IgD & IgE
A: IgG & IgM
Answer: A: IgG & IgM 
Explanation: None