Complete the following sentence :
When sound travels in a medium, the particles of medium .............. but the disturbance ………………….. .

Explanation

To complete the sentence: "When sound travels in a medium, the particles of medium **vibrate** but the disturbance **travels**."

### Step-by-Step Solution:

1. **Understanding the Movement of Particles**:
- When sound travels through a medium (solid, liquid, or gas), the particles of that medium do not move from their original positions. Instead, they oscillate or vibrate around their equilibrium positions.

2. **Identifying the Nature of Disturbance**:
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