Explanation:

- Xerophthalmia is a medical condition characterized by dry eyes and is primarily caused by a deficiency in Vitamin A.

- Vitamin A is essential for maintaining healthy vision, immune function, and skin health. A lack of it can lead to xerophthalmia.

- Vitamin D is crucial for bone health and immune function, but it does not relate to xerophthalmia.

- Vitamin C is important for skin health and immune support, and deficiency can lead to scurvy, not xerophthalmia.

- Vitamin K is essential for blood clotting and bone health, not for preventing xerophthalmia.

Correct Answer: Option 3 - A