**Core Concept**
Vitamin C deficiency, also known as scurvy, is a condition characterized by the inadequate production of collagen due to the lack of ascorbic acid. This deficiency affects several body systems, particularly the musculoskeletal, cardiovascular, and integumentary systems. The absence of ascorbic acid leads to the impaired hydroxylation of proline and lysine residues in collagen, resulting in the characteristic signs of scurvy.

**Why the Correct Answer is Right**
The correct answer is related to the clinical manifestations of scurvy. The signs of scurvy include:

* Sclerotic changes in the blood vessels (arteriosclerosis)
* Poor wound healing
* Periarticular hemorrhages and joint pain
* Impaired collagen synthesis leading to gum disease and loosening of teeth

**Why Each Wrong Option is Incorrect**
**Option A:** The "ground-glass" appearance of the lungs is actually a radiological sign of silicosis, not scurvy.
**Option B:** The "beading" or "tram-track" appearance of the aorta is a characteristic sign of scurvy due to the sclerotic changes in the blood vessels.
**Option C:** The "ring sign" is a radiological feature of scurvy, indicating the presence of periarticular hemorrhages.
**Option D:** The "ground-glass" appearance of the lungs is not a sign of scurvy, but rather a characteristic feature of other conditions such as silicosis.

**Clinical Pearl / High-Yield Fact**
The classic "four Ds" of scurvy are:
* **Deficiency** of vitamin C
* **Dyspnea** (difficulty breathing)
* **Dizziness** (due to poor wound healing and impaired collagen synthesis)
* **Decubitus** ulcers (bedsores)

**Correct Answer: C. The "ground-glass" appearance of the lungs is actually a radiological sign of silicosis, not scurvy.**