**Core Concept**
Total lung capacity (TLC) is the maximum volume of air present in the lungs after maximum inhalation. It is a crucial parameter in assessing respiratory function and is influenced by factors such as lung volume, chest wall compliance, and airway resistance.

**Why the Correct Answer is Right**
The correct answer is related to the concept of lung volume and its components. TLC is the sum of tidal volume (Vt), inspiratory reserve volume (IRV), and expiratory reserve volume (ERV). The formula for TLC is: TLC = Vt + IRV + ERV. This formula highlights the importance of understanding the individual components of lung volume in determining TLC.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not directly relate to the definition of TLC. While lung compliance is an important factor in determining TLC, it is not the primary factor.

**Option B:** This option is incorrect because airway resistance is a factor that affects the rate of airflow, but not the volume of air present in the lungs.

**Option C:** This option is incorrect because the diaphragm is a critical muscle involved in respiratory function, but it is not directly related to the calculation of TLC.

**Clinical Pearl / High-Yield Fact**
A key point to remember is that TLC can be affected by various conditions such as respiratory diseases, obesity, and neuromuscular disorders, which can alter lung volume and compliance.

**Correct Answer: D. Lung volume