**Core Concept**
Transthoracic compliance refers to the change in lung volume resulting from a given change in intrapleural pressure. It is an essential parameter in understanding respiratory mechanics and is crucial for clinicians to assess lung function, especially in patients with respiratory diseases.

**Why the Correct Answer is Right**
The transthoracic compliance formula is derived from the equation: Compliance (C) = Change in Lung Volume (ΔV) / Change in Intrapleural Pressure (ΔP). This formula represents the ability of the lungs and chest wall to expand and fill with air. The correct formula is C = ΔV / ΔP, where ΔV is the change in lung volume and ΔP is the change in intrapleural pressure.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it represents the work done in expanding the lungs, not the compliance. Work of breathing is an essential concept in respiratory physiology but is not related to the transthoracic compliance formula.
**Option B:** This option is incorrect because it represents the resistance to airflow in the airways, not the compliance. Airway resistance is an important concept in respiratory physiology but is not related to the transthoracic compliance formula.
**Option C:** This option is incorrect because it represents the time constant of the respiratory system, not the compliance. The time constant is an important concept in respiratory physiology but is not related to the transthoracic compliance formula.

**Clinical Pearl / High-Yield Fact**
The transthoracic compliance is reduced in conditions such as pulmonary fibrosis, chronic obstructive pulmonary disease (COPD), and pneumothorax. Clinicians should be aware of these conditions and their effects on lung compliance to provide appropriate management and treatment.

**Correct Answer: C. ΔV / ΔP**