**Core Concept**
Primary tuberculosis (TB) is the initial infection caused by Mycobacterium tuberculosis, typically affecting the lungs. It is characterized by a specific set of pathological features that distinguish it from post-primary or secondary TB.

**Why the Correct Answer is Right**
The apical lung cavity is more commonly associated with post-primary TB, where the disease has reactivated and caused extensive tissue destruction and cavitation. In contrast, primary TB typically presents with smaller, more discrete lesions, such as Ghon's focus, which is a primary complex consisting of a pulmonary lesion (usually an upper lobe consolidation) and a corresponding lymph node enlargement. The primary TB lesion is usually not as extensive as the cavities seen in post-primary TB. Paratracheal lymphadenopathy is indeed a feature of primary TB, as the primary complex often involves the hilar lymph nodes, which are located near the trachea.

**Why Each Wrong Option is Incorrect**
**Option B:** Ghon's focus is a characteristic feature of primary TB, representing the primary complex of the disease.
**Option C:** Paratracheal lymphadenopathy is also a feature of primary TB, as the primary complex often involves the hilar lymph nodes near the trachea.
**Option D:** Primary TB can indeed heal spontaneously by fibrosis, as the body's immune response often contains the infection, leading to scarring and resolution of the disease.

**Clinical Pearl / High-Yield Fact**
Primary TB typically presents with a more localized and contained lesion, such as Ghon's focus, whereas post-primary TB is characterized by more extensive tissue destruction and cavitation.

**✓ Correct Answer: A. Apical lung cavity**