Choose the correct one of the following regarding respiratory capacities is

Options

A. FRC = ERV+RV
B. VC = IC - ERV
C. IC = ERV+ VC
D. EC = IC - ERV

Answer

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

### Step-by-Step Solution:

1. **Understanding FRC (Functional Residual Capacity)**:
- FRC is defined as the volume of air remaining in the lungs after a normal expiration.
- Mathematically, FRC is the sum of two volumes:
- ERV (Expiratory Reserve Volume) - the amount of air that can be forcibly exhaled after a normal exhalation.
- RV (Residual Volume) - the amount of air that remains in the lungs after a maximal exhalation.
- Therefore, the equation for FRC is:
\[ FRC = ERV + RV \]
- This option is **correct**.

2. **Analyzing VC (Vital Capacity)**:
- VC is the maximum amount of air that can be exhaled after a maximum inhalation.
- It is calculated as the sum of:
- TV (Tidal Volume) - the amount of air inhaled or exhaled during normal breathing.
- ERV (Expiratory Reserve Volume).
- IRV (Inspiratory Reserve Volume) - the amount of air that can be inhaled after a normal inhalation.
- The correct equation for VC is:
\[ VC = TV + ERV + IRV \]
- The statement "VC is equal to IC minus ERV" is **incorrect**.

3. **Evaluating IC (Inspiratory Capacity)**:
- IC is the maximum amount of air that can be inhaled after a normal expiration.
- It is the sum of:
- TV (Tidal Volume)
- IRV (Inspiratory Reserve Volume).
- The equation for IC is:
\[ IC = TV + IRV \]
- The statement "IC is equal to ERV plus VC" is **incorrect**.

4. **Examining EC (Expiratory Capacity)**:
- EC refers to the total amount of air that can be exhaled after a normal inhalation.
- It is the sum of:
- ERV (Expiratory Reserve Volume)
- TV (Tidal Volume).
- The equation for EC is:
\[ EC = ERV + TV \]
- The statement "EC is equal to IC minus ERV" is **incorrect**.

### Conclusion:
After analyzing all the options, the only correct statement regarding respiratory capacities is:
\[ \text{FRC = ERV + RV} \]

### Final Answer:
The correct option is: **FRC is equal to ERV plus RV**.