Dermatitis, diarrhoea and dementia are seen in deficiency of

$\text{Correct option:C}$ 

$\text{Solution:}$

$\text{Option (A)}$

$\bullet$ Thiamine ($B_1$) deficiency leads to beriberi disease,Wernicke syndrome,Korsakoff syndrome in alcoholic.

$\bullet$ It is essential for growth and repair of tissues,helps to convert tryptophan to niacin and acts as thiamine pyrophophate in TCA cycle.

$\text{Option (B)}$

$\bullet$ Riboflavin($B_2$) deficiency leads to cheilosis ,it helps in erythrocytes production,acts as flavin mononucleotide in electron transport chain and FAD in Krebs cycle.

$\text{Option (C)}$

$\bullet$ Niacin($B_3$) deficiency results in pellagra ,diarrhoea ,dermatitis ,hartnup disease(hereditary disease which leads to inability in the metabolism of tryptophan). It acts as NAD and NADP in Krebs cycle.

$\text{Option (D)}$

$\bullet$ Foliate($B_{1}0$) deficiency causes megaloblastic anemia as it is a primary raw material in the production and maturation of erythrocytes. It checks on the synthesis,proper functioning of neurological system.

$\text{Hence, the correct option is (C)}$