Assertion : Alcohol and petrol can be used as household fuels for cooking.
Reason : They are not highly inflammable substances.

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

To solve the question, we need to analyze both the assertion and the reason provided.

### Step-by-Step Solution:

1. **Understanding the Assertion**:
- The assertion states that "Alcohol and petrol can be used as household fuels for cooking."
- This statement is **incorrect** because alcohol and petrol are not suitable for household cooking due to their properties.

**Hint**: Consider the safety and combustion characteristics of fuels used in households.

2. **Understanding the Reason**:
- The reason states that "They are not highly inflammable substances."
- This statement is also **incorrect**. Alcohol and petrol are actually highly inflammable substances, meaning they can easily catch fire.

**Hint**: Recall the definition of inflammable substances and their ignition temperatures.

3. **Ignition Temperature**:
- Both alcohol and petrol have a low ignition temperature, which means they ignite easily and can cause dangerous fires.
- Household fuels should ideally have a moderate ignition temperature to ensure safety during cooking.

**Hint**: Think about what properties make a fuel safe for cooking in a household environment.

4. **Conclusion**:
- Since both the assertion and the reason are false, we conclude that the correct answer is that both the assertion and the reason are false.

**Hint**: Review the options provided in the question to identify the correct one based on your conclusions.

### Final Answer:
Both assertion and reason are false.

### Options Analysis:
- Option 1: Both assertion and reason are true and reason is correct explanation for assertion. **(False)**
- Option 2: Both assertion and reason are true but reason is not correct explanation for assertion. **(False)**
- Option 3: Assertion is true, reason is false. **(False)**
- Option 4: Both assertion and reason are false. **(True)**

Thus, the answer is **Option 4**.