Sound can travel in........

Explanation

**Step-by-Step Solution:**

1. **Understanding Sound**: Sound is defined as the vibration of matter. It is created by the movement of particles in a medium.

2. **Requirement of a Medium**: For sound to travel, it needs a medium. This is because sound waves are produced by the vibrations of particles, and these vibrations need to be transferred from one particle to another.

3. **Types of Mediums**: The medium through which sound travels can be in different forms:
- **Solid**: Sound travels well in solids because the particles are closely packed and can easily transfer vibrations.
...