The correct answer is option 3: rickets. Rickets is a condition that occurs due to a deficiency of vitamin D in children. Vitamin D plays a crucial role in the body`s absorption of calcium and phosphorus, which are necessary for the development and maintenance of healthy bones and teeth. When there is a deficiency of vitamin D, it leads to impaired calcium and phosphorus absorption, resulting in weakened and soft bones. Children with rickets may experience symptoms such as bowed legs, delayed growth, or deformities in the skeletal structure. Beriberi (option 1) is caused by a deficiency of vitamin B1, pellagra (option 2) is caused by a deficiency of niacin, and scurvy (option 4) is caused by a deficiency of vitamin C.