Explanation:

- Pellagra is a disease resulting from a deficiency of Vitamin B3, also known as niacin. Symptoms include diarrhea, dermatitis, and dementia.

- Option 1: B3 - This is the correct answer. Pellagra is directly linked to the lack of this vitamin.

- Option 2: B6 - This vitamin deficiency can lead to anemia, depression, or confusion, but not pellagra.

- Option 3: B2 - A deficiency in Vitamin B2, or riboflavin, may cause skin disorders, sores around the mouth, and anemia, but it does not cause pellagra.

- Option 4: B12 - Often associated with anemia and neurological issues when deficient, but not with pellagra.

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