The inspiratory reserve volume `+` tidal volume `+` expiratory reserve volume is the same as

Options

A. inspiratory capacity `+` expiratory reserve volume
B. total lung capacity `-` funcational residual capacity
C. inspiratory capacity `+` functional residual capacity
D. inspiratory capacity `+` residual volume.

Explanation

To solve the question, we need to understand the definitions of the different lung volumes and how they relate to each other. The question asks for the sum of the inspiratory reserve volume (IRV), tidal volume (TV), and expiratory reserve volume (ERV).

### Step-by-Step Solution:

1. **Define the Volumes**:
- **Tidal Volume (TV)**: The amount of air inhaled or exhaled during normal breathing.
- **Inspiratory Reserve Volume (IRV)**: The additional amount of air that can be inhaled after a normal inhalation.
- **Expiratory Reserve Volume (ERV)**: The additional amount of air that can be exhaled after a normal exhalation.

2. **Sum the Volumes**:
- We need to find the sum of these three volumes:
\[ \text{Total} = \text{IRV} + \text{TV} + \text{ERV} \]

3. **Identify the Equivalent Capacity**:
- The sum of IRV and TV gives us the **Inspiratory Capacity (IC)**, which is the maximum amount of air that can be inhaled after a normal expiration:
\[ \text{IC} = \text{IRV} + \text{TV} \]
- Therefore, the total can be expressed as:
\[ \text{Total} = \text{IC} + \text{ERV} \]

4. **Conclusion**:
- The sum of the inspiratory reserve volume, tidal volume, and expiratory reserve volume is equal to the **Inspiratory Capacity (IC) plus Expiratory Reserve Volume (ERV)**.
- This is equivalent to the definition of **Vital Capacity (VC)**, which is the maximum amount of air a person can expel from the lungs after a maximum inhalation:
\[ \text{VC} = \text{IRV} + \text{TV} + \text{ERV} \]

### Final Answer:
The inspiratory reserve volume + tidal volume + expiratory reserve volume is equal to the **Vital Capacity (VC)**.