Prolonged deficiency of nicotinic acid produces

The correct option is C Pellagra

• Vitamin $B_3$ or Niacin (Nicotinic Acid) is a water soluble vitamin essential for normal cellular metabolism as it is precursor of co-enzymes nicotinamide adenine dinucleotide (NAD) and nicotinamide adenine dinucleotide phosphate (NADP).
• Its deficiency causes a disease which is characterized with scaly, pigmented skin, irritation of the GI tract (diarrhea), known as Pellagra.
  

Hence, Option C is correct.