The amount of air that enters lungs during normal respiration is :

Options

A. tidal volume
B. vital capacity
C. total lung capacity
D. inspiratory capacity

Explanation

To determine the amount of air that enters the lungs during normal respiration, we can follow these steps:

### Step-by-Step Solution:

1. **Understand Normal Respiration**: Normal respiration refers to the process of breathing that occurs without any forceful effort. This is also known as tidal breathing.

2. **Identify the Relevant Term**: In the context of respiratory volumes, we need to identify the term that describes the volume of air exchanged during normal breathing.

3. **Define Tidal Volume**: The specific term that describes the amount of air entering the lungs during normal respiration is called "tidal volume."

4. **Quantify Tidal Volume**: For an average adult, the tidal volume is approximately 500 ml of air per breath.

5. **Differentiate from Other Respiratory Volumes**: It is important to distinguish tidal volume from other respiratory volumes such as:
- **Vital Capacity**: The maximum amount of air that can be exhaled after a maximum inhalation.
- **Total Lung Capacity**: The total volume of air the lungs can hold.
- **Inspiratory Capacity**: The maximum volume of air that can be inhaled after a normal expiration.

6. **Conclusion**: Based on the definition and average measurement, the amount of air that enters the lungs during normal respiration is **tidal volume**, which is around **500 ml**.

### Final Answer:
The amount of air that enters the lungs during normal respiration is **tidal volume**, approximately **500 ml**.

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