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
False about complement is 
Select and explain. 
A. Group of proteins normally found is serum, B. Constitute about 20% of normal serum proteins, C. Heat labile, D. Species non-specific
B: Constitute about 20% of normal serum proteins
Answer: B: Constitute about 20% of normal serum proteins 
Explanation: Constitute about 5% of normal serum proteins.