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
Chemical nature of complement is 
Select and explain. 
A. Lipid, B. Polysaccharide, C. Lipo polysaccharide, D. Protein
D: Protein
Answer: D: Protein 
Explanation: Complement is a protein in normal human and animal serum activated by antigen-antibody reactions Ref: Textbook of Microbiology Baveja 5th ed Pg 125