Sound travels in air if :

Options

A. particles of medium travel from one place to another
B. there is no moisture in the atmosphere
C. disturbance moves
D. both particles as well as disturbance travel from one place to another

Explanation

To solve the question "Sound travels in air if:", we need to analyze the options provided and understand the nature of sound propagation in a medium like air.

### Step-by-Step Solution:

1. **Understanding Sound Propagation**:
- Sound is a mechanical wave that requires a medium (like air) to travel. It cannot travel through a vacuum.
- When sound travels, it does so by creating disturbances in the medium.

2. **Analyzing the Options**:
- **Option a**: "the particles of medium travel from one place to another."
- This is incorrect. In sound propagation, the particles of the medium do not travel from one place to another; they vibrate around their equilibrium positions.

- **Option b**: "there is no moisture in the atmosphere."
- This is also incorrect. Sound can travel in moist air; moisture does not prevent sound from traveling.

- **Option c**: "the disturbance moves."
- This is correct. Sound travels because the disturbance (or wave) created by vibrating particles moves through the medium, transferring energy from one particle to the next.

- **Option d**: "both particle as well as disturbance travel from one place to another."
- This is incorrect. Only the disturbance travels, while the particles themselves remain in their positions and only vibrate.

3. **Conclusion**:
- The correct answer is **Option c**: "the disturbance moves." This means that sound travels in air when the disturbance created by the vibration of particles moves through the medium.

### Final Answer:
Sound travels in air if the disturbance moves.

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