This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Biochemistry
Deficiency of which vitamin causes glossitis, dementia, roughed keratotic areas on skin and gastrointestinal symptoms? 
Select and explain. 
A. Riboflavin, B. Pyridoxine, C. Niacin, D. Pantothenic acid
C: Niacin
Answer: C: Niacin 
Explanation: None