Expiratory capacity is

Options

A. tidal volume
B. expiratory reserve volume
C. residual volume
D. sum of tidal volume and expiratory reserve volume

Answer

**Step-by-Step Solution:**

1. **Understanding Expiratory Capacity**:
- Expiratory capacity refers to the total volume of air that can be exhaled from the lungs at one time.

2. **Components of Expiratory Capacity**:
- It includes both normal exhalation and forceful exhalation.
- Normal exhalation is defined as tidal volume.

3. **Defining Tidal Volume**:
- Tidal volume is the amount of air that is inhaled or exhaled during normal breathing without any force.

4. **Defining Expiratory Reserve Volume**:
- Expiratory reserve volume is the additional amount of air that can be forcibly exhaled after the end of a normal exhalation.

5. **Calculating Expiratory Capacity**:
- Expiratory capacity can be calculated as the sum of tidal volume and expiratory reserve volume.
- Formula: Expiratory Capacity = Tidal Volume + Expiratory Reserve Volume.

6. **Conclusion**:
- Therefore, the expiratory capacity is the total volume of air that can be exhaled, which is the sum of the tidal volume and the expiratory reserve volume.

**Final Answer**: Expiratory capacity is the sum of tidal volume and expiratory reserve volume.

---