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: Social & Preventive Medicine
[{'content': 'Niacin deficiency cause \nSelect and explain. \nA. Pellagra, B. Scurvy, C. Rickets, D. Lathyrism', 'role': 'user'}, {'content': "Answer: A \nExplanation: Niacin \n\nThis vitamin differs from the other vitamins of the B-complex group in that an essential amino acids tryptophan serves as its precursor.\nAnother characterstic of niacin is that it is not excreted in urine as such, but is metabolised to two major methylated derivatives.\n\n\nN-methyl-nicotinamide\nN-methyl pyridones\n\n\nNiacin deficiency results in *Pellagra ’\nPellagra is identified by the presence of three 'D's → Diarrhea, Dementia, Dermatitis.", 'role': 'assistant'}]