Dermatitis, diarrhoea and dementia are seen in deficiency of `:-`

Options

A. Thiamine
B. Riboflavin
C. Niacin
D. Foliate

Answer

### Step-by-Step Solution:

1. **Understanding the Symptoms**: The question lists three symptoms: dermatitis, diarrhea, and dementia. These symptoms need to be associated with a specific vitamin deficiency.

2. **Identifying the Disease**: The combination of dermatitis, diarrhea, and dementia is characteristic of a condition known as pellagra. Pellagra is often referred to as the "three D's" disease because of these symptoms.

3. **Linking Symptoms to Vitamin Deficiency**: Pellagra is caused by a deficiency of Vitamin B3, which is also known as niacin. This vitamin is essential for various metabolic processes in the body.

4. **Evaluating the Options**:
- **Thiamine (Vitamin B1)**: Deficiency leads to beriberi, which is not associated with the three symptoms mentioned.
- **Riboflavin (Vitamin B2)**: Deficiency can cause symptoms like fatigue and issues with iron absorption, but not the three D's.
- **Niacin (Vitamin B3)**: Correctly associated with pellagra, leading to dermatitis, diarrhea, and dementia.
- **Folate (Vitamin B9)**: Deficiency can lead to megaloblastic anemia, which does not include the three D's.

5. **Conclusion**: Based on the evaluation, the correct answer is niacin (Vitamin B3), as it is the vitamin whose deficiency leads to the symptoms of dermatitis, diarrhea, and dementia.

### Final Answer:
Dermatitis, diarrhea, and dementia are seen in deficiency of **niacin (Vitamin B3)**.

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