This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: All India exam, Subject name: Medicine
The following condition is caused by the deficiency of? 
Select and explain. 
A. vitamin A, B. vitamin B, C. Vitamin C, D. vitamin D
A: vitamin A
Answer: A: vitamin A 
Explanation: Bitot&;s spots are the buildup of keratin located superficially in the conjunctiva of human&;s eyes. They can be oval, triangular or irregular in shape. The spots are a sign of vitamin A deficiency and associated with drying of the cornea. ref : harrisons 20th ed