Spirometer can not measure

Options

A. Tital volume
B. Vital capacity
C. Expiratory reserve volume
D. Residual volume

Answer

### Step-by-Step Solution:

1. **Understanding Spirometer**: A spirometer is a device used to measure the volume of air inhaled and exhaled by the lungs. It helps in assessing lung function and respiratory health.

2. **Identifying Measurable Volumes**:
- **Tidal Volume**: This is the amount of air that is inhaled or exhaled during normal breathing. It can be measured using a spirometer.
- **Vital Capacity**: This is the maximum amount of air that can be exhaled after taking the deepest breath possible. It is also measurable with a spirometer.
- **Expiratory Reserve Volume**: This refers to the maximum volume of air that can be forcibly exhaled after the end of a normal expiration. This can be measured by a spirometer as well.

3. **Understanding Residual Volume**: Residual volume is the amount of air that remains in the lungs after a maximal exhalation. This volume cannot be measured directly by a spirometer because it involves the air that is always present in the lungs and cannot be exhaled.

4. **Conclusion**: Therefore, the spirometer cannot measure the residual volume, as it is not possible to exhale this air from the lungs.

### Final Answer:
**A spirometer cannot measure residual volume.**

---