Assertion : The angle of contact of a lilquid with a solid decreases with increase in temperature.
Reason : With increase in temperature, the surface tension of the liquid increases.

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 and reason is false.
D. If both assertion and reason are false.

Explanation

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

**Assertion:** The angle of contact of a liquid with a solid decreases with an increase in temperature.
**Reason:** With an increase in temperature, the surface tension of the liquid increases.

### Step-by-step Solution:

1. **Understanding the Angle of Contact:**
The angle of contact (or contact angle) is the angle formed between the tangent to the liquid surface and the solid surface at the point of contact. It indicates how well a liquid wets a solid surface.

2. **Effect of Temperature on Surface Tension:**
Surface tension is a property of liquids that arises due to cohesive forces between liquid molecules. As temperature increases, the kinetic energy of the molecules also increases, leading to greater molecular motion. This increased motion reduces the cohesive forces between the molecules, which in turn decreases the surface tension of the liquid.

3. **Relationship Between Surface Tension and Angle of Contact:**
Generally, a decrease in surface tension leads to a decrease in the angle of contact for most liquids. This means that as temperature increases and surface tension decreases, the angle of contact typically decreases, indicating better wetting of the solid surface.

4. **Evaluating the Assertion:**
The assertion states that the angle of contact decreases with an increase in temperature. Based on the relationship established in the previous step, this assertion is generally true for most liquids.

5. **Evaluating the Reason:**
The reason states that with an increase in temperature, the surface tension of the liquid increases. However, we have established that surface tension actually decreases with an increase in temperature. Therefore, the reason is false.

6. **Conclusion:**
Since the assertion is true and the reason is false, we conclude that the correct answer is:
- Assertion is true.
- Reason is false.

### Final Answer:
- Assertion: True
- Reason: False