A : Efficiency of heat engine can neve be 100%.
R : Second law of thermodynamics puts a limitaion of the efficiency of a heat engine.

Options

A. If both Assertion & Reason are true and the reason is the correct explantion of the assertion, then mark(1)
B. If both Assertion & Reason are true but the reason is not the correct explanation of the assertion, then mark (2).
C. If Assertion is true statement but Reason is false, then mark (3).
D. If both Assertion and Reason are false statements, then mark (4)

Answer

To solve the assertion-reason question, we need to analyze both the assertion (A) and the reason (R) provided.

### Step-by-Step Solution:

1. **Understanding the Assertion (A)**:
- The assertion states that "the efficiency of a heat engine can never be 100%."
- This statement is true. The efficiency of a heat engine is defined as the ratio of work output to heat input. According to the laws of thermodynamics, specifically the second law, it is impossible for any heat engine to convert all the heat energy absorbed into work without some energy being lost to the surroundings.

2. **Understanding the Reason (R)**:
- The reason states that "the second law of thermodynamics puts a limitation on the efficiency of a heat engine."
- This statement is also true. The second law of thermodynamics implies that in any energy exchange, some energy is always lost as waste heat, which prevents the efficiency from reaching 100%. The maximum efficiency of a heat engine is given by the Carnot efficiency formula:
\[ \eta = 1 - \frac{T_2}{T_1} \]
where \(T_1\) is the absolute temperature of the heat source and \(T_2\) is the absolute temperature of the heat sink. For efficiency to be 100%, \(T_2\) would need to be 0 K (absolute zero), which is unattainable.

3. **Conclusion**:
- Since both the assertion and the reason are true, we need to determine the relationship between them. The reason correctly explains why the assertion is true. Therefore, the correct answer is that both the assertion and the reason are true, and the reason is a correct explanation of the assertion.

### Final Answer:
Both A and R are true, and R is the correct explanation for A.