Choose the correct statement.

Options

A. Scientific principle involved in refrigerator is laws of thermodynamics
B. Scientific principle involved in steam engine is laws of thermodynamics
C. Scientific principle involved in rocket propulsion is Newton's laws of motion
D. All of these

Answer

To solve the question of which statement is correct, we will evaluate each of the four options provided.

### Step-by-Step Solution:

1. **Evaluate the First Option:**
- The first option states that "the scientific principle involved in the refrigerator is the law of thermodynamics."
- This statement is correct because refrigerators operate based on the first law of thermodynamics, which deals with the conservation of energy and the transfer of heat.

2. **Evaluate the Second Option:**
- The second option states that "in steam engine, the first law of thermodynamics is used."
- This statement is also correct as steam engines convert heat energy into mechanical work, adhering to the first law of thermodynamics.

3. **Evaluate the Third Option:**
- The third option states that "the scientific principle used in rocket propulsion is Newton's law of motion."
- This statement is correct as rocket propulsion is fundamentally based on Newton's third law of motion, which states that for every action, there is an equal and opposite reaction.

4. **Evaluate the Fourth Option:**
- The fourth option claims that "all the above statements are correct."
- Since we have established that the first, second, and third options are all correct, this statement is also correct.

### Conclusion:
- Therefore, the correct answer is **Option 4**, which states that all the above statements are correct.