**Core Concept**
Total lung capacity (TLC) is the maximum volume of air present in the lungs after maximum inhalation. It is the sum of tidal volume, inspiratory reserve volume, and expiratory reserve volume. TLC is an essential parameter in pulmonary function tests, reflecting the lung's ability to expand and hold air.

**Why the Correct Answer is Right**
The correct answer is the sum of the residual volume, inspiratory reserve volume, tidal volume, and expiratory reserve volume. This is because TLC represents the total volume of air in the lungs after a maximal inhalation. The inspiratory and expiratory reserve volumes are added to the tidal volume, and the residual volume is included as it is the volume of air remaining in the lungs after a maximal exhalation.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect as it does not include the residual volume, which is a crucial component of total lung capacity.
**Option B:** This option is incorrect as it only includes the inspiratory and expiratory reserve volumes and does not account for the tidal volume.
**Option C:** This option is incorrect as it only includes the residual volume and does not account for the other components of total lung capacity.

**Clinical Pearl / High-Yield Fact**
It is essential to remember that TLC is an important parameter in assessing lung function, particularly in conditions like chronic obstructive pulmonary disease (COPD) and pulmonary fibrosis. A reduced TLC may indicate lung damage or restrictive lung disease.

**Correct Answer:** D. Residual volume + Inspiratory reserve volume + Tidal volume + Expiratory reserve volume.