The volume of the air involved in breathing movements can be estimated by using

Options

A. Spherometer
B. Sphygmomanometer
C. Spirometer
D. Voltmeter

Answer

To solve the question regarding the volume of air involved in breathing movements, we need to identify the correct instrument from the given options. Let's go through the options step by step:

### Step-by-Step Solution:

1. **Understanding the Question**: The question asks for a device that can estimate the volume of air involved in breathing movements.

2. **Evaluating Option A - Pherometer**: The first option is "pherometer." This device is not commonly associated with measuring air volume in breathing. Instead, it is incorrectly referenced here. Thus, this option is incorrect.

3. **Evaluating Option B - Sphygmomanometer**: The second option is "sphygmomanometer." This device is specifically used to measure blood pressure, not the volume of air in breathing. Therefore, this option is also incorrect.

4. **Evaluating Option C - Spirometer**: The third option is "spirometer." A spirometer is a device that measures the volume of air inhaled and exhaled by the lungs. It records the changes in volume and movement of air out of the lungs, making it the correct choice for estimating the volume of air involved in breathing movements.

5. **Evaluating Option D - Voltmeter**: The fourth option is "voltmeter." This device measures electrical voltage and has no relevance to measuring air volume in breathing. Thus, this option is incorrect.

6. **Conclusion**: After evaluating all options, the correct answer is **Option C - Spirometer**, as it is the instrument specifically designed for measuring the volume of air involved in breathing movements.

### Final Answer:
The volume of the air involved in breathing movements can be estimated by using a **spirometer**.