Assertion : Carbon dioxide produced by burning of fuels causes global warming.
Reason : It leads to melting of polar ice.

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.

Explanation

### Step-by-Step Solution:

1. **Understand the Assertion**: The assertion states that "Carbon dioxide produced by burning of fuels causes global warming." This is a true statement because carbon dioxide (CO2) is a greenhouse gas that contributes to the greenhouse effect, which leads to an increase in Earth's temperature.

**Hint**: Recall what greenhouse gases are and how they affect Earth's temperature.

2. **Understand the Reason**: The reason states that "It leads to melting of polar ice." This statement is also true. Global warming results in rising temperatures, which can cause polar ice to melt.

**Hint**: Think about the consequences of rising temperatures on polar regions.

3. **Analyze the Relationship**: While both the assertion and the reason are true, we need to determine if the reason is the correct explanation for the assertion. The assertion explains that CO2 causes global warming, while the reason explains one of the effects of global warming (melting of polar ice). Therefore, the reason does not directly explain why CO2 causes global warming.

**Hint**: Consider whether the reason directly supports the assertion or if it simply describes a consequence of the assertion.

4. **Conclusion**: Since both the assertion and reason are true, but the reason is not the correct explanation for the assertion, the correct answer is that both are true, but the reason is not the correct explanation for the assertion.

**Hint**: Look for options that specify the truth of both statements without linking them as cause and effect.

### Final Answer:
The correct option is: "Both assertion and reason are true, but reason is not the correct explanation for assertion."