A rise in `P_(CO_(2))` increases the oxygen - affinity of haemoglobin.

Answer

To solve the question regarding the relationship between the rise in partial pressure of carbon dioxide (P_CO2) and the oxygen affinity of hemoglobin, we can follow these steps:

### Step-by-Step Solution:

1. **Understand Hemoglobin's Role**: Hemoglobin is a protein in red blood cells that binds to oxygen, forming oxyhemoglobin. It can carry up to four molecules of oxygen.

2. **Identify Factors Affecting Oxygen Binding**: Several factors influence the binding of oxygen to hemoglobin, including:
- Partial Pressure of Oxygen (P_O2)
- Partial Pressure of Carbon Dioxide (P_CO2)
- Concentration of Hydrogen Ions (H+)
- Temperature

3. **Analyze the Effect of P_CO2**:
- When the partial pressure of carbon dioxide increases, it leads to a decrease in the affinity of hemoglobin for oxygen. This is due to the Bohr effect, where increased CO2 levels result in a lower pH (more acidic conditions), which reduces hemoglobin's ability to bind oxygen.

4. **Conclusion**: Therefore, the statement "A rise in P_CO2 increases the oxygen-affinity of hemoglobin" is incorrect. In fact, an increase in P_CO2 decreases the oxygen affinity of hemoglobin.

### Final Answer:
The statement is false; a rise in P_CO2 decreases the oxygen affinity of hemoglobin.

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