Which statement is wrong ?

Options

A. Partial pressure of `CO_2(PCO_2)` is higher in the air inside the lungs
B. Partial pressure of `O_2(PC_2)` is higher in the air inside the lungs
C. Partial pressure of `O_2(PC_2)` is lower inside the venous blood than in the air in the lung
D. Partial pressure of `CO_2(PCO_2)` is higher inside the venous blood than in the air

Answer

To determine which statement is wrong regarding the exchange of gases in the respiratory system, we need to analyze each statement based on our understanding of gas exchange and the partial pressures of oxygen (O2) and carbon dioxide (CO2).

### Step-by-Step Solution:

1. **Understanding Gas Exchange**: The primary function of the respiratory system is to facilitate the exchange of gases—oxygen and carbon dioxide—between the atmosphere and the body's tissues. This process occurs in the alveoli of the lungs.

2. **Concentration Gradient**: Gas exchange occurs along the concentration gradient. Oxygen moves from areas of higher concentration (atmospheric air) to areas of lower concentration (lungs and blood), while carbon dioxide moves from areas of higher concentration (blood and tissues) to areas of lower concentration (lungs and atmospheric air).

3. **Analyzing the Statements**:
- **Statement A**: "Carbon dioxide is more in air than in lungs."
- This statement is incorrect because the concentration of CO2 in the atmosphere is much lower than in the lungs, where CO2 accumulates from the body's metabolic processes.

- **Statement B**: "Oxygen is more in the air than in the lungs."
- This statement is correct. The air we breathe contains a higher concentration of oxygen compared to the oxygen present in the lungs.

- **Statement C**: "Oxygen in our blood is less than air."
- This statement is also correct. The venous blood returning to the lungs has a lower concentration of oxygen compared to the atmospheric air.

- **Statement D**: "Carbon dioxide is more than air in the blood."
- This statement is correct as well. The concentration of CO2 in the blood is higher than in the atmospheric air.

4. **Conclusion**: The only incorrect statement among the options provided is Statement A.

### Final Answer:
**The wrong statement is: "Carbon dioxide is more in air than in lungs." (Statement A)**