**Core Concept**
Spontaneous pneumothorax occurs when air enters the pleural space without any external cause, leading to lung collapse. The primary goal of treatment is to re-expand the lung and prevent further complications.

**Why the Correct Answer is Right**
The earliest treatment of choice for spontaneous pneumothorax is needle aspiration or insertion of a chest tube, also known as thoracostomy. This procedure is performed to evacuate the air from the pleural space, allowing the lung to re-expand. The procedure is typically done under local anesthesia, and the patient is usually monitored for signs of tension pneumothorax or other complications.

**Why Each Wrong Option is Incorrect**
**Option A:** Oxygen therapy alone is not sufficient to treat spontaneous pneumothorax, as it may worsen the condition by increasing the volume of air in the pleural space.
**Option B:** Surgical repair of the lung is generally reserved for patients with recurrent spontaneous pneumothorax or those who are candidates for thoracoscopic surgery.
**Option C:** Positive pressure ventilation may exacerbate the condition by increasing the pressure in the pleural space, potentially leading to further lung collapse.

**Clinical Pearl / High-Yield Fact**
For patients with spontaneous pneumothorax, it's essential to quickly identify the cause of the pneumothorax and address any underlying conditions that may have contributed to its development, such as Marfan syndrome or chronic obstructive pulmonary disease (COPD).

**Correct Answer:** C. Chest tube insertion.