**Core Concept**
Inspiratory capacity (IC) is the maximum volume of air that can be inhaled after a normal exhalation. It is the sum of the tidal volume (TV) and inspiratory reserve volume (IRV).

**Why the Correct Answer is Right**
Inspiratory capacity is crucial for determining the body's ability to take in oxygen during increased physical activity or respiratory demands. The inspiratory capacity is calculated as IC = TV + IRV. The inspiratory reserve volume is the additional volume of air that can be inhaled above the normal tidal volume. This is essential for maintaining adequate oxygenation during periods of increased respiratory need.

**Why Each Wrong Option is Incorrect**
**Option A:** Incorrect, as the inspiratory capacity does not include the expiratory reserve volume (ERV) or the residual volume (RV). These volumes are part of the expiratory reserve volume, not the inspiratory capacity.
**Option B:** Incorrect, as the inspiratory capacity does not equal the vital capacity (VC). The vital capacity is the maximum volume of air that can be exhaled after maximum inhalation.

**Clinical Pearl / High-Yield Fact**
It is essential to distinguish between inspiratory capacity and vital capacity, as inspiratory capacity is used to assess respiratory function in patients with respiratory diseases such as chronic obstructive pulmonary disease (COPD).

**Correct Answer:** C. Inspiratory capacity equals tidal volume plus inspiratory reserve volume.