Concept:Pellagra is a deficiency disease caused by a lack of niacin (vitamin B3) or its precursor tryptophan.
Explanation:Niacin helps the body produce energy by forming coenzymes NAD and NADP.
Without enough niacin, the body cannot carry out key metabolic functions.
This leads to pellagra, which is known for the “4 Ds”: dermatitis (skin rash), diarrhoea, dementia, and death if untreated.
Common causes include poor diet, alcoholism, and conditions that reduce niacin absorption.
Among the given options, only niacin deficiency causes pellagra. Riboflavin causes ariboflavinosis, folic acid causes anaemia, and calcium deficiency affects bones.
Answer:C. niacin