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: Pathology
Most important bactericidal agent is 
Select and explain. 
A. Cationic basic protein, B. Lactoferrin, C. Lysozyme, D. Reactive O2 species
D: Reactive O2 species
Answer: D: Reactive O2 species 
Explanation: H2O2- MPO- halide system is the most efficient bactericidal system of neutrophils