Increase in concentration of one of the following immediately affects human beings because it affects `O_(2)` carrying capacity of haemoglobin.

Options

A. `CO_(2)`
B. `SO_(2)`
C. `CO`
D. `SO_(4)`

Answer

**Step-by-Step Solution:**

1. **Understanding the Question**: The question asks which substance, when its concentration increases, affects human beings by impacting the oxygen-carrying capacity of hemoglobin.

2. **Identifying the Options**: The options provided are:
- 1. Carbon Dioxide (CO₂)
- 2. Sulphur Dioxide (SO₂)
- 3. Carbon Monoxide (CO)

3. **Analyzing Each Option**:
- **Carbon Dioxide (CO₂)**: While increased levels of CO₂ can lead to respiratory issues and affect overall health, it does not directly bind to hemoglobin to reduce its oxygen-carrying capacity.
- **Sulphur Dioxide (SO₂)**: This gas can cause respiratory problems and irritation but does not significantly affect hemoglobin's ability to carry oxygen.
- **Carbon Monoxide (CO)**: This is a toxic gas that binds with hemoglobin much more effectively than oxygen. When CO binds to hemoglobin, it forms carboxyhemoglobin, which reduces the amount of hemoglobin available to carry oxygen, leading to decreased oxygen levels in the blood.

4. **Conclusion**: Based on the analysis, the correct answer is **Carbon Monoxide (CO)**, as it directly affects the oxygen-carrying capacity of hemoglobin by forming carboxyhemoglobin.

**Final Answer**: Carbon Monoxide (CO)

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