Sound in air propagates in form of:

Options

A. longitudinal wave
B. transverse wave
C. both longitudinal and transverse waves
D. neither longitudinal nor transverse wave.

Explanation

To solve the question "Sound in air propagates in form of:", we will analyze the nature of sound waves and their propagation in air.

### Step-by-Step Solution:

1. **Understanding Sound Waves**:
- Sound is a mechanical wave that requires a medium to travel. It cannot propagate in a vacuum.

2. **Types of Waves**:
- There are two main types of waves: longitudinal waves and transverse waves.
- **Longitudinal Waves**: In these waves, the particle displacement is parallel to the direction of wave propagation. This means that as the wave travels, the particles of the medium move back and forth in the same direction as the wave.
- **Transverse Waves**: In these waves, the particle displacement is perpendicular to the direction of wave propagation. This means that as the wave travels, the particles move up and down while the wave moves horizontally.

3. **Sound Propagation in Air**:
- In air, sound travels through the process of compressions and rarefactions.
- **Compressions**: Areas where particles are close together.
- **Rarefactions**: Areas where particles are spread apart.
- As sound travels, air particles oscillate back and forth in the same direction as the sound wave, which is characteristic of longitudinal waves.

4. **Conclusion**:
- Since sound in air is characterized by particle motion that is parallel to the direction of wave propagation, it is classified as a longitudinal wave.

5. **Final Answer**:
- Therefore, the correct option is: Sound in air propagates in the form of **longitudinal waves**.