**Core Concept:** Oxygen therapy is a medical procedure that increases oxygen delivery to tissues in patients with hypoxemia, respiratory insufficiency, or other conditions affecting oxygenation. It can be used for various purposes, such as supplementing oxygen for normal respiratory processes, improving arterial oxygen saturation, or preventing or treating hypoxemia.

**Why the Correct Answer is Right:**
The correct answer, Positive End-Expiratory Pressure (PEEP), is a component of mechanical ventilation that helps to prevent atelectasis (falling apart of lung tissue) and re-expands collapsed alveoli in patients with acute respiratory distress syndrome (ARDS) or other acute respiratory failure conditions. By increasing the functional residual capacity and decreasing the work of breathing, PEEP improves oxygenation and ventilation-perfusion matching.

**Why Each Wrong Option is Incorrect:**
A. Non-invasive Ventilation (NIV) is a form of assisted ventilation that uses a face mask or nasal prongs to provide oxygen therapy and support ventilation. NIV does not directly address the issue of PEEP, making it an incorrect choice.
B. Continuous Positive Airway Pressure (CPAP) is a form of non-invasive ventilation that provides a constant pressure to the airways to maintain patency and improve oxygenation. While CPAP may be used as a first-line intervention, it does not specifically address the issue of PEEP, making it an incorrect choice.
C. High-Flow Nasal Cannula (HFNC) delivers a high flow of warm, humidified oxygen to patients with respiratory distress. Although HFNC can improve oxygenation and reduce work of breathing, it does not directly address the issue of PEEP, making it an incorrect choice.
D. Mechanical Ventilation is a more advanced respiratory support technique where the ventilator delivers a controlled breath for patients who are unable to breathe independently. While mechanical ventilation can be used to provide PEEP, it is not a standalone therapy for PEEP, making it an incorrect choice.

**Clinical Pearl:** PEEP is a crucial component of mechanical ventilation, particularly in patients with acute respiratory distress syndrome (ARDS) or other acute respiratory failure conditions. It is essential to understand when to use which ventilation strategy (e.g., CPAP, HFNC, or mechanical ventilation) and when to use PEEP to optimize patient outcomes in respiratory distress scenarios.