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
Which of the following is present in Paneth cells? 
Select and explain. 
A. Zinc, B. Copper, C. Molybdenum, D. Selenium
A: Zinc
Answer: A: Zinc 
Explanation: Paneth cells, located in the basal poion of the intestinal crypts below the stem cells, are exocrine cells with large, eosinophilic secretory granules in their apical cytoplasm. The granules contain the bactericidal enzyme lysozyme, an arginine-rich protein, and zinc. Paneth cell granules undergo exocytosis to release lysozyme, phospholipase A2, and hydrophobic peptides called defensins, all of which bind and breakdown membranes of microorganisms and bacterial walls. Paneth cells have an impoant role in innate immunity and in regulating the microenvironment of the intestinal crypts. Ref: Mescher A.L. (2010). Chapter 15. Digestive Tract. In A.L. Mescher (Ed), Junqueira's Basic Histology: Text & Atlas, 12e.