<prompt> The following condition is caused by the deficiency of?vitamin Avitamin BVitamin Cvitamin D  <response>: 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 