Which of the following is a sink for CO?

Options

A. Haemoglobin
B. Microorganisms present in the soil
C. Oceans
D. Plants

Answer

To determine which of the following options acts as a sink for carbon monoxide (CO), we first need to understand what a "sink" is in environmental chemistry. A sink is a medium in the environment that absorbs or consumes pollutants, either partially or completely.

### Step-by-Step Solution:

1. **Understanding Carbon Monoxide (CO)**:
- Carbon monoxide is a colorless, odorless gas that is a pollutant in the environment. It is produced from incomplete combustion of carbon-containing fuels.

2. **Identifying the Options**:
- The options provided are:
- A. Hemoglobin
- B. Microorganisms present in the soil
- C. Oceans
- D. Plants

3. **Evaluating Hemoglobin**:
- Hemoglobin is a protein in red blood cells that binds to oxygen. While it can bind to carbon monoxide, it does not act as a sink for CO in the environmental context. Instead, it transports CO in the bloodstream.

4. **Evaluating Microorganisms in Soil**:
- Microorganisms present in the soil can metabolize carbon monoxide. They utilize CO as a carbon source, effectively reducing its concentration in the environment. Therefore, they act as a sink for carbon monoxide.

5. **Evaluating Oceans**:
- Oceans do not significantly absorb carbon monoxide. While they can absorb various gases, CO is not one of them in a meaningful way.

6. **Evaluating Plants**:
- Plants primarily absorb carbon dioxide (CO2) during photosynthesis and do not act as a significant sink for carbon monoxide.

7. **Conclusion**:
- Based on the evaluations, the correct answer is that microorganisms present in the soil act as a sink for carbon monoxide.

### Final Answer:
**Microorganisms present in the soil** are the sink for carbon monoxide.

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