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
Cathelicidins are rich in which of the following amino acid? 
Select and explain. 
A. Cysteine, B. Cystine, C. Methionine, D. Arginine
D: Arginine
Answer: D: Arginine 
Explanation: Microbial killing can also occur through the action of other substances in leukocyte granules. Cationic arginine-rich granule peptides that are toxic to microbes; cathelicidins is present in leukocyte granules. Ref: Robbins 8th edition, Chapter 2.