**Core Concept**
Surfactant action in the lungs is crucial for reducing surface tension, thereby facilitating easier lung expansion and preventing alveolar collapse during expiration. This phenomenon is governed by a specific physical principle.

**Why the Correct Answer is Right**
The correct answer is related to **Young-Laplace Law**, which describes the relationship between the pressure difference across a curved surface and its surface tension. In the context of pulmonary surfactant, the Young-Laplace Law explains how surfactant molecules reduce the surface tension at the air-liquid interface, making it easier for alveoli to expand during inspiration.

• Surfactant molecules aggregate at the air-liquid interface, forming a monolayer.
• This monolayer reduces the surface tension, allowing for easier alveolar expansion.
• The Young-Laplace Law quantitatively describes this phenomenon, highlighting the importance of surface tension in lung mechanics.

**Why Each Wrong Option is Incorrect**
**Option A:** Not applicable, as it is related to a different physiological process.
**Option B:** Incorrect, as it pertains to a different physical principle governing fluid dynamics.
**Option C:** Incorrect, as it is related to a different aspect of lung physiology, such as gas exchange.

**Clinical Pearl / High-Yield Fact**
Surfactant deficiency or dysfunction can lead to respiratory distress syndrome (RDS) in preterm infants, highlighting the critical role of surfactant in lung function.

**Correct Answer: C. Young-Laplace Law.**