**Core Concept**
Medusa head sign is a radiological finding seen in pulmonary tuberculosis, characterized by a central mass with multiple small nodules or cavities resembling the snake hair of Medusa from Greek mythology. This sign is a classic radiographic feature of miliary tuberculosis.

**Why the Correct Answer is Right**
The Medusa head sign is due to the widespread dissemination of tuberculosis bacilli in the lungs, leading to the formation of numerous small granulomas. These granulomas can be seen as small nodules or cavities on chest radiographs, giving the characteristic appearance. The central mass represents the primary site of infection, while the surrounding nodules represent the spread of the disease.

**Why Each Wrong Option is Incorrect**
**Option A:** Not applicable (no information provided)
**Option B:** Not relevant to the Medusa head sign
**Option C:** Not a characteristic feature of pulmonary tuberculosis

**Clinical Pearl / High-Yield Fact**
The Medusa head sign is a classic radiographic feature of miliary tuberculosis, a form of tuberculosis characterized by the widespread dissemination of the disease. It is essential to recognize this sign in patients with suspected TB to initiate appropriate treatment.

**Correct Answer: C. Pulmonary tuberculosis**