**Core Concept**
Sarcoidosis is a systemic granulomatous disease characterized by the formation of non-caseating granulomas in various organs, including the lungs, skin, and lymph nodes. The exact pathogenesis of sarcoidosis is unknown, but it is believed to result from a dysregulated immune response to an unidentified antigen.

**Why the Correct Answer is Right**
The correct answer is a feature of sarcoidosis because it is a hallmark of the disease. Non-caseating granulomas are formed as a result of the accumulation of macrophages and T-lymphocytes in response to an unknown antigen. This leads to the formation of granulomas, which are characteristic of sarcoidosis. The lungs are the most commonly affected organ, but sarcoidosis can also affect the skin, lymph nodes, and other organs.

**Why Each Wrong Option is Incorrect**
**Option A:** Eosinophilia is not a feature of sarcoidosis. Sarcoidosis is characterized by an increase in lymphocytes, particularly CD4+ T-lymphocytes, but not eosinophils.

**Option B:** Hypercalcemia is a feature of sarcoidosis. The increased levels of vitamin D3 produced by macrophages in granulomas can lead to increased absorption of calcium, resulting in hypercalcemia.

**Option C:** Nodular pulmonary fibrosis is a feature of sarcoidosis. Chronic inflammation in the lungs can lead to the formation of nodules and fibrosis, which can result in pulmonary fibrosis.

**Clinical Pearl / High-Yield Fact**
It's essential to remember that sarcoidosis can present with a wide range of symptoms, including respiratory, skin, and eye manifestations. A high index of suspicion is necessary for diagnosis, and a thorough clinical evaluation, along with imaging studies and histopathological examination, is required for confirmation.

**Correct Answer:** A.