Vital capacity of lungs is

Options

A. `IRV + ERV`
B. `IRV + ERV + TV - RV`
C. `IRV + ERV + Tv + RV`
D. `IRV + ERV + TV`.

Explanation

**Step-by-Step Solution:**

1. **Definition of Vital Capacity:**
- Vital capacity refers to the maximum amount of air that can be inhaled after a forcible expiration. It is an important measure of lung function.

2. **Components of Vital Capacity:**
- Vital capacity is calculated by adding three specific lung volumes:
- **Inspiratory Reserve Volume (IRV):** This is the additional amount of air that can be inhaled after a normal inhalation.
- **Expiratory Reserve Volume (ERV):** This is the additional amount of air that can be exhaled after a normal exhalation.
- **Tidal Volume (TV):** This is the normal amount of air that is inhaled or exhaled during regular breathing.

3. **Formula for Vital Capacity:**
- The formula for calculating vital capacity (VC) can be expressed as:
\[ VC = IRV + ERV + TV \]

4. **Conclusion:**
- Therefore, the vital capacity of the lungs is the sum of the inspiratory reserve volume, expiratory reserve volume, and tidal volume.

5. **Answer Option:**
- Based on the explanation, the correct answer is option D, which states that vital capacity is the sum of inspiratory reserve volume, expiratory reserve volume, and tidal volume.

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