Assertion: In case of collision of gas molecules in a given amount of gas, total kinetic energy is conserved.
Reason: All collisions of the gas molecules in a given amount of gas are elastic.

Options

A. If both assertion and reason are true and reason is the correct explanation os assertion.
B. If both assertion and reason are true but reason is not be 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 given question, we need to analyze both the assertion and the reason provided.

### Step-by-Step Solution:

1. **Understanding the Assertion**:
- The assertion states that in the case of collisions of gas molecules in a given amount of gas, the total kinetic energy is conserved.
- This implies that when gas molecules collide, the sum of their kinetic energies before the collision is equal to the sum of their kinetic energies after the collision.

2. **Understanding the Reason**:
- The reason provided states that all collisions of gas molecules in a given amount of gas are elastic.
- An elastic collision is defined as a collision in which both momentum and kinetic energy are conserved.

3. **Linking Assertion and Reason**:
- According to the kinetic theory of gases, one of the fundamental assumptions is that all collisions between gas molecules (and between molecules and the walls of the container) are elastic.
- Since the collisions are elastic, it follows that both momentum and kinetic energy are conserved during these collisions.

4. **Conclusion**:
- Since the reason correctly explains the assertion, we can conclude that both the assertion and the reason are true.
- Therefore, the correct answer is that both the assertion and reason are true, and the reason is the correct explanation of the assertion.

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

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