This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: JIPMER 2017, Subject name: Medicine
In Vitamin A deficiency, respiratory tract infection due to: 
Select and explain. 
A. Keratinization of upper epithelial cells, B. Lack of antibody production, C. Dysfunction of epithelial layer, D. Defective chemotaxis
C: Dysfunction of epithelial layer
Answer: C: Dysfunction of epithelial layer 
Explanation: Vitamin A: - Role 1) Vision 2) Reproduction & growth 3) Maintenance of epithelial cell 4) Stabilization of cellular and intra Cellular membrane 5) Synthesis of glycoprotein 6) Antioxidant 7) Skin & Bone Metabolism