Assertion : Carbon dioxide is used as a fire extinguisher.
Reason : Fire can be extinguished by cutting off the supply of oxygen.

Options

A. If both assertion and reason are true and reason is the correct explanation of assertion.
B. If both assertion and reason are true but reason is not the correct explanation of assertion.
C. If assertion is true but reason is false.
D. If both assertion and reason are false.

Answer

### Step-by-Step Solution:

1. **Identify the Assertion and Reason**:
- Assertion: Carbon dioxide is used as a fire extinguisher.
- Reason: Fire can be extinguished by cutting off the supply of oxygen.

2. **Evaluate the Assertion**:
- Carbon dioxide (CO2) is indeed used as a fire extinguisher. It is effective because it does not support combustion and can displace oxygen around a fire.

3. **Evaluate the Reason**:
- The reason states that fire can be extinguished by cutting off the supply of oxygen. This is true because fire requires oxygen to sustain combustion. Without oxygen, the fire cannot continue to burn.

4. **Connect the Assertion and Reason**:
- The assertion (CO2 as a fire extinguisher) is supported by the reason (cutting off oxygen extinguishes fire). When CO2 is released, it blankets the fire and reduces the oxygen concentration, effectively extinguishing the fire.

5. **Conclusion**:
- Both the assertion and the reason are true, and the reason correctly explains why the assertion is true. Therefore, the correct answer is that both the assertion and reason are true, and the reason is the correct explanation for the assertion.

### Final Answer:
- The correct option is: Both assertion and reason are true, and reason is the correct explanation for assertion.

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