**Core Concept**
The patient's symptoms and history of exposure to Mycobacterium tuberculosis (M. tuberculosis) suggest a diagnosis of tuberculosis (TB) reactivation. The lung pathology associated with TB is characterized by an immune response to the bacterium, leading to the formation of granulomas.

**Why the Correct Answer is Right**
Granulomas are aggregates of immune cells, including macrophages, lymphocytes, and epithelioid cells, that form in response to chronic inflammation and infection. In the context of TB, granulomas are a hallmark of lung pathology, resulting from the body's attempt to contain and eliminate the M. tuberculosis bacteria. The presence of granulomas is a key diagnostic feature of TB, and they can be seen on histopathological examination of lung tissue.

**Why Each Wrong Option is Incorrect**
**Option A:** Dense fibrosis is a feature of chronic lung diseases, such as pulmonary fibrosis, but it is not a characteristic of TB pathology.

**Option B:** Eosinophilic infiltration is typically seen in parasitic infections or allergic reactions, and is not a feature of TB.

**Option D:** Plasma cell infiltration is a feature of chronic infections, such as subacute bacterial endocarditis, but it is not a characteristic of TB pathology.

**Clinical Pearl / High-Yield Fact**
TB granulomas can be classified into several types, including caseating granulomas (also known as necrotizing granulomas), which are characteristic of TB, and non-caseating granulomas, which are seen in other conditions such as sarcoidosis.

**✓ Correct Answer: C. Granulomas**