Assertion (A) At critical temperature liquid passes into gaseous state imperceptibly and continuously.
Reason (R) The density of liquid and gaseous phase is equal to critical temperature.

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

### Step-by-Step Solution:

1. **Understanding Critical Temperature (Tc)**:
- Critical temperature is the temperature above which a substance cannot exist in the liquid state, regardless of the pressure applied. At this temperature, the properties of the liquid and gas phases become indistinguishable.

2. **Assertion Analysis**:
- The assertion states that "At critical temperature, liquid passes into gaseous state imperceptibly and continuously." This means that as the temperature reaches the critical point, the transition from liquid to gas does not have a distinct phase change; it happens smoothly.

3. **Reason Analysis**:
- The reason provided states that "The density of liquid and gaseous phase is equal at critical temperature." This is a key point because when the densities of the two phases become equal, it allows for a smooth transition without a distinct boundary between the liquid and gas phases.

4. **Connecting Assertion and Reason**:
- Since at the critical temperature, the densities of the liquid and gaseous phases are equal, this equality allows the liquid to transition to gas without a noticeable change. Hence, the assertion is supported by the reason.

5. **Conclusion**:
- Both the assertion (A) and the reason (R) are correct. Furthermore, the reason (R) provides a correct explanation for the assertion (A). Therefore, the statement is validated.

### Final Answer:
Both the assertion and the reason are correct, and the reason correctly explains the assertion.

---