Assertion : Sound waves travel in the form of compressions and rarefactions in air.
Reason : Because crests and troughs cannot be sustained in air, therefore, sound waves cannot travel through air in the form of transverse waves.

Options

A. If both assertion and reason are correct and reason is a correct explanation of the assertion.
B. If both assertion and reason are correct but reason is not the correct explanation of assertion.
C. If assertion is correct but reason is incorrect
D. If assertion is incorrect but reason is correct.

Answer

To solve the question, we need to analyze both the assertion and the reason provided, and determine their validity.

### Step 1: Analyze the Assertion
The assertion states: "Sound waves travel in the form of compressions and rarefactions in air."

- **Explanation**: Sound waves are longitudinal waves, which means they consist of regions where particles are close together (compressions) and regions where they are spread apart (rarefactions). This is a fundamental characteristic of how sound propagates through a medium like air.

**Conclusion for Step 1**: The assertion is true.

### Step 2: Analyze the Reason
The reason states: "Because crests and troughs cannot be sustained in air, therefore, sound waves cannot travel through air in the form of transverse waves."

- **Explanation**: Transverse waves are characterized by oscillations that are perpendicular to the direction of wave propagation. In a medium like air, which is a gas, there is insufficient restoring force to support the formation of crests and troughs, which are essential for transverse waves. This lack of elasticity in air means that sound cannot propagate as a transverse wave.

**Conclusion for Step 2**: The reason is also true.

### Step 3: Determine the Relationship
Now we need to establish if the reason correctly explains the assertion.

- The assertion is about how sound waves travel (as compressions and rarefactions), while the reason explains why sound cannot travel as transverse waves (due to the inability to sustain crests and troughs in air). The reason provides a valid explanation for the assertion.

### Final Conclusion
Both the assertion and the reason are correct, and the reason is indeed the correct explanation for the assertion.

### Answer:
Both assertion and reason are correct, and the reason is the correct explanation of the assertion.

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