Which of the following factors is not favourable for the formation of oxyhaemoglobin ?

Options

A. High `PO_(2)`
B. Low temperature
C. Less `H^(+)` concentration
D. High `PCO_(2)`

Explanation

To determine which factor is not favorable for the formation of oxyhemoglobin, we need to analyze each option provided in the question.

### Step-by-Step Solution:

1. **Understanding Oxyhemoglobin Formation**: Oxyhemoglobin is formed when oxygen binds to hemoglobin in red blood cells. The efficiency of this binding is influenced by several factors including partial pressure of oxygen, temperature, carbon dioxide levels, and hydrogen ion concentration.

2. **Analyzing Each Option**:
- **Option A: High Partial Pressure of Oxygen**: A high partial pressure of oxygen is favorable for the formation of oxyhemoglobin. This is because the greater the concentration of oxygen, the more likely it is to bind with hemoglobin.

- **Option B: Low Temperature**: Low temperature also favors the formation of oxyhemoglobin. Lower temperatures help maintain the binding of oxygen to hemoglobin, as high temperatures can lead to the dissociation of oxygen from hemoglobin.

- **Option C: Less Hydrogen Ion Concentration**: Less hydrogen ion concentration (which corresponds to a higher pH) is favorable for the formation of oxyhemoglobin. An increase in hydrogen ions (lower pH) promotes the release of oxygen from hemoglobin (Bohr effect).

- **Option D: High Partial Pressure of Carbon Dioxide**: High levels of carbon dioxide are not favorable for the formation of oxyhemoglobin. Increased carbon dioxide levels lead to a decrease in pH (more acidic conditions), which promotes the release of oxygen from hemoglobin.

3. **Conclusion**: The factor that is not favorable for the formation of oxyhemoglobin is **Option D: High Partial Pressure of Carbon Dioxide**.

### Final Answer:
**D. High Partial Pressure of Carbon Dioxide**

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