Select the correct option regarding respiratory volumes.

Options

A. `"Total capacity of lungs"= "Vital capacity "+" Tidal air "`
B. `"Vital capacity of lungs" = "Total lung capacity" -" Residual air"`
C. `"Vital capacity of lungs" =" Tidal air" + "Complemental air"`
D. `"Total capacity of lungs "= "Tidal air" +" Complemental air" +" Supplemental air"`

Answer

To solve the question regarding respiratory volumes, we need to analyze each option provided and determine which one is correct based on our understanding of lung capacities and volumes.

### Step-by-Step Solution:

1. **Understanding Total Lung Capacity (TLC)**:
- Total Lung Capacity is defined as the maximum amount of air the lungs can hold. It is the sum of all lung volumes.
- TLC = Residual Volume (RV) + Vital Capacity (VC).

2. **Analyzing the First Option**:
- The first option states: "Total capacity of lungs is equal to the vital capacity plus tidal air."
- This is incorrect because TLC includes residual volume, not just tidal air and vital capacity.

3. **Analyzing the Second Option**:
- The second option states: "Vital capacity of lungs is equal to total lung capacity minus residual air."
- This is correct because Vital Capacity (VC) is indeed calculated as TLC - RV.

4. **Analyzing the Third Option**:
- The third option states: "Vital capacity of lungs is equal to tidal air plus complemental air."
- This is incorrect. Vital Capacity is not simply the sum of tidal air and complemental air.

5. **Analyzing the Fourth Option**:
- The fourth option states: "Total capacity of lungs is equal to the tidal air plus complemental air plus supplemental air."
- This is also incorrect. Total Lung Capacity includes residual volume and is not defined by just these three components.

6. **Conclusion**:
- After analyzing all options, the correct answer is the second option: "Vital capacity of lungs is equal to total lung capacity minus residual air."

### Final Answer:
The correct option regarding respiratory volumes is **Option 2**: "Vital capacity of lungs is equal to total lung capacity minus residual air."