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: Biochemistry
Xerophthalmia is caused by: 
Select and explain. 
A. Vitamin A deficiency, B. Vitamin D deficiency, C. Vitamin C deficiency, D. Vitamin K deficiency
A: Vitamin A deficiency
Answer: A: Vitamin A deficiency 
Explanation: None