Correct Option: C. Rickets Detailed Explanation: Vitamin D is a crucial nutrient that plays a significant role in calcium and phosphorus metabolism, which are essential for maintaining healthy bones and teeth. When there is a deficiency of vitamin D, the body cannot absorb calcium effectively from the diet, leading to various health issues, particularly in children. Rickets is a condition that arises specifically due to a deficiency of vitamin D, calcium, or phosphate. It is characterized by the softening and weakening of bones in children, which can lead to deformities such as bowed legs, thickened wrists and ankles, and a protruding breastbone. The lack of vitamin D impairs the body's ability to maintain proper calcium levels, which is critical for bone mineralization. Mechanism of Rickets: 1. Vitamin D Synthesis: Vitamin D can be synthesized in the skin upon exposure to sunlight or obtained from dietary sources (like fatty fish, fortified dairy products, and egg yolks). 2. Calcium Absorption: Vitamin D promotes the absorption of calcium in the intestines. Without sufficient vitamin D, calcium absorption is reduced. 3. Bone Health: Calcium is vital for the formation and maintenance of bone structure. Inadequate calcium leads to the softening of bones, resulting in rickets. Why Other Options Are Incorrect:

• A. Scurvy: This condition is caused by a deficiency of vitamin C (ascorbic acid), not vitamin D. Scurvy leads to symptoms such as bleeding gums, weakness, and skin issues due to impaired collagen synthesis.
• B. Pellagra: Pellagra is caused by a deficiency of niacin (vitamin B3) and is characterized by the "three D's": dermatitis, diarrhea, and dementia. It is unrelated to vitamin D deficiency.
• D. Beriberi: This condition results from a deficiency of thiamine (vitamin B1). It affects the cardiovascular and nervous systems and is not associated with vitamin D levels.

Summary of Key Points:

• Vitamin D Deficiency: Leads to rickets, characterized by soft and weak bones in children.
• Mechanism: Vitamin D is essential for calcium absorption; without it, bones cannot mineralize properly.
• Other Deficiencies: Scurvy (vitamin C), Pellagra (niacin), and Beriberi (thiamine) are unrelated to vitamin D.

Revision Summary:

• Rickets is caused by vitamin D deficiency, leading to weak bones in children.
• Vitamin D is crucial for calcium absorption and bone health.
• Other options (scurvy, pellagra, beriberi) are linked to different vitamin deficiencies.
• Understanding the role of vitamins in the body helps in recognizing deficiency-related diseases.