**Core Concept**
Biotin is a water-soluble B-complex vitamin essential for various bodily functions, including energy production, nerve function, and skin health. Biotin deficiency can lead to dermatitis, glossitis, and alopecia due to its critical role in maintaining the integrity of skin, mucous membranes, and hair follicles.

**Why the Correct Answer is Right**
The correct answer, **Dermatitis, glossitis, Alopecia**, is a classic triad associated with biotin deficiency. Dermatitis refers to skin inflammation, often presenting as eczema or skin rashes. Glossitis is inflammation of the tongue, leading to redness, swelling, and a burning sensation. Alopecia, or hair loss, is a common symptom of biotin deficiency, affecting both hair growth and texture. This triad occurs due to biotin's crucial role in maintaining the health of skin, mucous membranes, and hair follicles.

**Why Each Wrong Option is Incorrect**
**Option A:** Steatorrhea, or fatty stools, is more commonly associated with fat-soluble vitamin deficiencies, such as vitamin E or vitamin K deficiencies. Steatorrhea is not a characteristic symptom of biotin deficiency.
**Option C:** Mental changes, diarrhea, and alopecia are not a recognized triad associated with biotin deficiency. Mental changes may be more related to other B-complex vitamin deficiencies, such as thiamine or folate deficiencies.
**Option D:** Dementia is not a symptom of biotin deficiency. Dementia is more commonly associated with other neurological disorders or vitamin deficiencies, such as vitamin B12 deficiency.

**Clinical Pearl / High-Yield Fact**
Biotin deficiency can be caused by a variety of factors, including a diet lacking biotin-rich foods (e.g., nuts, eggs, and whole grains), certain medications (e.g., anticonvulsants), and genetic disorders (e.g., holocarboxylase synthetase deficiency). Clinicians should consider biotin deficiency in patients presenting with skin, mucous membrane, or hair disorders, especially if they have a history of malabsorption or are taking potential biotin-interfering medications.

✓ Correct Answer: B. Dermatitis, glossitis, Alopecia