Which of these statements about the partial pressure of `CO_(2)`is true ?

Options

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

Explanation

To determine which statement about the partial pressure of carbon dioxide (CO₂) is true, we need to analyze the concentration of CO₂ in different locations during the process of respiration. Here’s a step-by-step breakdown:

### Step 1: Understand the Locations of CO₂ Concentration
- We need to consider three main areas: inspired air, alveolar air, and expired air.

### Step 2: Analyze CO₂ Concentration in Inspired Air
- Inspired air is the air that we breathe in. It has a very low concentration of CO₂, typically around 0.04% (or 0.3 mmHg).

### Step 3: Analyze CO₂ Concentration in Alveolar Air
- Alveolar air is the air present in the alveoli of the lungs, where gas exchange occurs. The concentration of CO₂ in alveolar air is approximately 5.3%.

### Step 4: Analyze CO₂ Concentration in Expired Air
- Expired air is the air that we breathe out. The concentration of CO₂ in expired air is about 3.6%.

### Step 5: Compare the Concentrations
- Now, let's compare the concentrations:
- Inspired air: ~0.04% CO₂
- Alveolar air: ~5.3% CO₂
- Expired air: ~3.6% CO₂

### Step 6: Determine the True Statement
- From our analysis:
- The concentration of CO₂ in alveolar air (5.3%) is higher than in expired air (3.6%).
- Therefore, the correct statement is: "There is more CO₂ in alveolar air than in expired air."

### Conclusion
- The correct answer is the second option: "more in alveolar air than in expired air."

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