**Core Concept**
Ghon's focus is a characteristic histopathological feature seen in primary pulmonary tuberculosis (TB). It represents a healed area of caseous necrosis in the lung parenchyma, typically found in the upper lobes.

**Why the Correct Answer is Right**
Ghon's focus is formed when the initial tuberculous infection is contained by the body's immune response, leading to the formation of a granuloma. This granuloma eventually heals, leaving behind a characteristic focus of caseous necrosis. The presence of a Ghon's focus is often associated with calcification and is a key diagnostic feature of primary pulmonary TB.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because Ghon's focus is not typically found in the lower lobes of the lung, where it is more common to find secondary or post-primary TB.
* **Option B:** This option is incorrect because Ghon's focus is not a feature of secondary or post-primary TB, which is characterized by a different set of histopathological features.
* **Option C:** This option is incorrect because Ghon's focus is not a feature of military TB, which is characterized by a widespread dissemination of TB bacilli throughout the body.

**Clinical Pearl / High-Yield Fact**
It's essential to remember that Ghon's focus is often associated with calcification, which can be visualized on chest X-rays. This can be a key diagnostic clue in patients with a history of TB exposure or symptoms suggestive of TB.

**Correct Answer: C. Middle lobe of the lung.**