Assertion : The ignition temperature of kerosene oil is lower than that of wood.
Reason: A combustible substance cannot catch fire as long as its temperature is lower than its ignition temperature.

Options

A. Both A and R are true, and R is correct explanation of the assertion.
B. Both A and R are true, but R is not the correct explanation of the assertion.
C. A is true, but R is false.
D. A is false, but R is true.

Explanation

To analyze the assertion and reason provided in the question, we will break it down step by step.

### Step 1: Understand the Assertion
The assertion states that "The ignition temperature of kerosene oil is lower than that of wood."

- **Ignition Temperature**: This is the minimum temperature at which a substance catches fire.
- **Comparison**: We need to compare the ignition temperatures of kerosene oil and wood.

### Step 2: Gather Information on Ignition Temperatures
- Kerosene oil typically has an ignition temperature of around 220°C.
- Wood has a higher ignition temperature, usually around 300°C.

### Step 3: Evaluate the Assertion
Since 220°C (kerosene oil) is lower than 300°C (wood), the assertion is **true**.

### Step 4: Understand the Reason
The reason states that "A combustible substance cannot catch fire as long as its temperature is lower than its ignition temperature."

- This means that for any combustible material, it will not ignite unless it reaches or exceeds its ignition temperature.

### Step 5: Evaluate the Reason
The reason is a general principle of combustion and is **true**. A combustible substance indeed requires a certain temperature (ignition temperature) to catch fire.

### Conclusion
Both the assertion and the reason are true. The assertion correctly states the relationship between the ignition temperatures of kerosene oil and wood, and the reason accurately describes the conditions necessary for combustion.

### Final Answer
**Both the assertion and the reason are true. The assertion is correct because kerosene oil has a lower ignition temperature than wood, and the reason is correct as it explains the conditions under which a combustible substance can ignite.**

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