`CO_(2)` concentration is

Options

A. More in expired air than in alveolar air
B. More in alveolar air than in expired air
C. More in inspired air than in alveolar air
D. More in inspired air than in expired air

Explanation

To determine the correct answer regarding the concentration of CO2 (carbon dioxide) in different types of air, we can follow these steps:

### Step 1: Understand the Types of Air
- **Inspired Air**: This is the air that we inhale from the atmosphere. It has a lower concentration of CO2 compared to the air in our lungs.
- **Alveolar Air**: This is the air present in the alveoli of the lungs where gas exchange occurs. It has a higher concentration of CO2 due to the exchange of gases.
- **Expired Air**: This is the air that we exhale. It contains more CO2 than inspired air but less than alveolar air.

### Step 2: Compare CO2 Concentration
- **Inspired Air vs. Alveolar Air**: Inspired air has a lower concentration of CO2 because it is fresh air from the atmosphere. Alveolar air has a higher concentration of CO2 because it is the result of gas exchange where CO2 from the blood enters the alveoli.

- **Alveolar Air vs. Expired Air**: Alveolar air has the highest concentration of CO2 because it is the air that has been in contact with the blood and has absorbed CO2. Expired air contains CO2 but is slightly diluted as it mixes with the fresh air from the atmosphere during exhalation.

### Step 3: Analyze the Options
- **Option A**: More in expired air than in alveolar air - Incorrect, as alveolar air has a higher concentration.
- **Option B**: More in alveolar air than in expired air - Correct, as alveolar air has the highest concentration of CO2.
- **Option C**: More in inspired air than in alveolar air - Incorrect, as inspired air has the lowest concentration.
- **Option D**: More in inspired air than in expired air - Incorrect, as expired air has more CO2 than inspired air.

### Conclusion
The correct answer is **Option B**: CO2 concentration is more in alveolar air than in expired air.

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