**Core Concept:** Scurvy is a disease caused by vitamin C deficiency, leading to impaired collagen synthesis, which affects blood vessels, bones, and joints.

**Why the Correct Answer is Right:** A definitive sign of scurvy in X-ray is increased bone density, specifically in the vertebrae and long bones. This occurs due to compensatory mechanism of increased bone deposition as the body tries to maintain mineral homeostasis.

**Why Each Wrong Option is Incorrect:**

A. **Increased joint space (OA/Rheumatoid arthritis):** The correct answer shows increased bone density, while increased joint space is associated with osteoarthritis or rheumatoid arthritis.

B. **Loss of bone mineral density (Osteoporosis):** Osteoporosis results in reduced bone density, not increased density.

C. **Normal bone density (Control/Normal):** A control group or a normal individual would not exhibit increased bone density, which is a characteristic feature of scurvy.

D. **Reduced bone density (Avascular necrosis):** Avascular necrosis leads to reduced bone density, unlike the increased density observed in scurvy.

**Clinical Pearl:** A definitive X-ray sign of scurvy helps in establishing the diagnosis when clinical features are not evident. Prompt treatment with vitamin C supplementation can prevent complications like hemorrhagic diathesis and joint destruction.

**Correct Answer:** **Option C: Normal bone density (Control/Normal)**

An X-ray of a patient with scurvy would show increased bone density, as explained above. In a control or normal individual, the bone density would be normal, making option C the correct answer.