Assertion : According to Le-Chatelier's -principle addition of heat to an equilibrium solid = liquid results in decrease in the amount of solid.
Reason : Reaction is endothemic, so on heating forward reaction is fovoured.

Options

A. if both assertion and reason are true and reason is thr 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 reson are false.

Explanation

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

### Step 1: Understand the Assertion
The assertion states that according to Le-Chatelier's principle, the addition of heat to an equilibrium between a solid and a liquid results in a decrease in the amount of solid.

**Explanation**:
- Le-Chatelier's principle states that if a system at equilibrium is subjected to a change in conditions (such as temperature, pressure, or concentration), the system will adjust itself to counteract that change and restore a new equilibrium.
- In this case, when heat is added to the equilibrium of solid and liquid, the system will shift to absorb that heat, which means it will favor the endothermic direction of the reaction, which is the conversion of solid to liquid.

### Step 2: Understand the Reason
The reason provided states that the reaction is endothermic, so on heating, the forward reaction is favored.

**Explanation**:
- An endothermic reaction is one that absorbs heat. In the context of the solid-liquid equilibrium, when heat is added, the system will favor the process that consumes heat, which is the melting of solid into liquid.
- Therefore, the addition of heat indeed favors the forward reaction (solid to liquid), leading to a decrease in the amount of solid present.

### Step 3: Conclusion
Both the assertion and the reason are true, and the reason correctly explains the assertion. Thus, the correct answer is that both statements are true, and the reason is the correct explanation of the assertion.

### Final Answer:
Both the assertion and the reason are true, and the reason is the correct explanation of the assertion.