Assertion : Waves produced in a cylinder containing a liquid by moving its piston back and forth are longitudinal waves.
Reason : In longitudinal waves, the particles of the medium oscillate parallel to the direction of propagation of the wave.

Options

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

Explanation

To solve the question, we will analyze the assertion and reason provided, and determine their validity.

### Step 1: Understand the Assertion
The assertion states that "waves produced in a cylinder containing a liquid by moving its piston back and forth are longitudinal waves."

- **Analysis**: When a piston moves back and forth in a cylinder filled with liquid, it creates pressure variations in the liquid. These pressure variations cause the particles of the liquid to move in the same direction as the wave propagation, which is characteristic of longitudinal waves.

### Step 2: Understand the Reason
The reason states that "in longitudinal waves, the particles of the medium oscillate parallel to the direction of propagation of the wave."

- **Analysis**: This statement is true. In longitudinal waves, the displacement of the medium's particles is indeed parallel to the direction in which the wave travels. This is consistent with the behavior of particles in the liquid when the piston moves back and forth.

### Step 3: Determine the Relationship Between Assertion and Reason
Now, we need to determine if the reason correctly explains the assertion.

- **Analysis**: While both the assertion and the reason are true, the reason does not specifically explain why the waves produced in the cylinder are longitudinal waves. The assertion is based on the behavior of the particles in the liquid due to the movement of the piston, while the reason provides a general definition of longitudinal waves.

### Conclusion
- **Final Answer**: Both the assertion and reason are true, but the reason is not the correct explanation of the assertion. Therefore, the correct option is that both assertion and reason are true, but the reason is not the correct explanation of the assertion.

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