Carbon monoxide kills becauses it destroyes.

Options

A. Haemoglobin
B. Phytochrome
C. Cytochrome
D. both A and B

Answer

**Step-by-Step Solution:**

1. **Understanding Carbon Monoxide (CO)**: Carbon monoxide is a colorless, odorless gas that is produced by burning fossil fuels. It is known for its harmful effects on human health.

2. **Mechanism of Action**: Carbon monoxide has a higher affinity for hemoglobin than oxygen does. This means that when both gases are present, carbon monoxide will preferentially bind to hemoglobin.

3. **Impact on Hemoglobin**: When carbon monoxide binds to hemoglobin, it forms carboxyhemoglobin. This binding prevents hemoglobin from carrying oxygen throughout the body.

4. **Consequences of Binding**: The binding of carbon monoxide to hemoglobin leads to a decrease in the amount of oxygen transported in the bloodstream. This results in a state of hypoxia, where the body and vital organs do not receive enough oxygen.

5. **Health Effects**: Prolonged exposure to carbon monoxide can lead to serious health issues, including suffocation, unconsciousness, and ultimately death, due to the lack of oxygen needed for cellular respiration.

6. **Conclusion**: Therefore, the correct answer to the question "Carbon monoxide kills because it destroys" is option A, which is hemoglobin.