Answer : 4. "Kwashiorkor"
Explanation :

(D) Kwashiorkor

Kwashiorkor is a disease caused by a deficiency of protein in the diet. It often occurs in areas where there is a lack of access to an adequate protein source. The condition is more common in developing countries and can affect children, leading to symptoms such as swelling (edema), a distended abdomen, stunted growth, and changes in skin and hair. Protein is essential for the proper growth and maintenance of tissues in the body, and a lack of it can result in severe health issues, as seen in the case of kwashiorkor. Scurvy, Beri-Beri, and Night-Blindness are caused by deficiencies of vitamin C, thiamine (vitamin B1), and vitamin A, respectively, not protein.