Xerophthalmia is a deficiency disease characterized by dryness of the eyes and is caused by a lack of Vitamin A. Vitamin A is an essential nutrient that plays a crucial role in maintaining eye health. It helps in the production of a pigment called rhodopsin, which is necessary for good vision in low light conditions. A deficiency of Vitamin A can lead to various eye problems, including night blindness and eventually xerophthalmia. Vitamin B, Vitamin C, and Vitamin D do not directly contribute to the development of xerophthalmia. Vitamin B is involved in the production of energy and cell metabolism, Vitamin C is important for immune function and collagen synthesis, while Vitamin D is essential for calcium absorption and bone health. Therefore, the correct option is 1 - Vitamin A.