Assertion (A) Gases do not liquefy above their critical temperature, even on applying high pressure.
Reason (R) Above critical temperature, the molecular speed is high and intermolecular attractions cannot hold the molecules together because they escape because of high speed.

Options

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

Explanation

To solve the assertion-reason question, we will analyze both the assertion (A) and the reason (R) step by step.

### Step-by-Step Solution:

1. **Understanding the Assertion (A)**:
- The assertion states: "Gases do not liquefy above their critical temperature, even on applying high pressure."
- This statement is **true**. The critical temperature is the temperature above which a gas cannot be liquefied, regardless of the pressure applied.

2. **Understanding the Reason (R)**:
- The reason states: "Above critical temperature, the molecular speed is high and intermolecular attractions cannot hold the molecules together because they escape because of high speed."
- This statement is also **true**. At temperatures above the critical temperature, the kinetic energy of the molecules is so high that the intermolecular forces (which are responsible for the attraction between molecules) become negligible. As a result, the molecules cannot come together to form a liquid.

3. **Connecting the Assertion and Reason**:
- The reason provided explains why the assertion is true. The high molecular speed at temperatures above the critical temperature prevents the intermolecular forces from holding the molecules together, thus preventing liquefaction.
- Therefore, the reason is a correct explanation of the assertion.

4. **Conclusion**:
- Both the assertion (A) and the reason (R) are true, and the reason correctly explains the assertion. Thus, the correct option is that both the assertion and reason are true, and the reason is the correct explanation for the assertion.

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

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