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 question, we need to evaluate the statements regarding the efficiency of a heat engine and the second law of thermodynamics.

### Step-by-Step Solution:

1. **Understanding the Assertion (A)**:
The assertion states that "the efficiency of a heat engine can never be 100%". This is a fundamental principle in thermodynamics.

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 law indeed states that not all input energy can be converted into work; some energy is always lost as waste heat.

3. **Analyzing the Carnot Efficiency Formula**:
The efficiency (η) of a Carnot engine is given by the formula:
\[ \eta = 1 - \frac{T_2}{T_1} \]
where \(T_1\) is the absolute temperature of the hot reservoir and \(T_2\) is the absolute temperature of the cold reservoir.

4. **Exploring Conditions for 100% Efficiency**:
For the efficiency to be 100% (η = 1), we would need:
\[ 1 - \frac{T_2}{T_1} = 1 \implies \frac{T_2}{T_1} = 0 \]
This implies that \(T_2\) must be 0 K (absolute zero), which is unattainable according to the third law of thermodynamics. Alternatively, \(T_1\) would have to be infinite, which is also not feasible.

5. **Conclusion on the Assertion and Reason**:
Since both the assertion (A) and the reason (R) are true, and the reason correctly explains why the assertion is true, we conclude that both statements are correct.

6. **Final Answer**:
Therefore, the correct option is that both assertion and reason are true, and the reason explains the assertion.