This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: All India exam, Subject name: Pathology
What is the percentage of immunoglobulins present in proteins 
Select and explain. 
A. 5-10%, B. 10-15%, C. 15-20%, D. 20-25%
C: 15-20%
Answer: C: 15-20% 
Explanation: Immunoglobulins constitute 20 to 25% of total serum proteins. Based on physiochemical and antigenic differences, five classes of immunoglobulins have been recognized: IgG, IgA, IgM, IgD, and IgE.(Ref: Ananthanarayan 9th edition, p93)