The sound waves travel fastest:

Options

A. solids
B. liquids
C. gases
D. vacuum

Explanation

To determine where sound waves travel fastest, we can analyze the properties of sound waves in different mediums: solids, liquids, gases, and vacuum.

### Step-by-Step Solution:

1. **Understanding Sound Waves**:
Sound waves are mechanical waves that require a medium to travel through. The speed of sound depends on the medium's properties, such as density and elasticity.

2. **Comparing Solids, Liquids, and Gases**:
- **Solids**: In solids, particles are closely packed together and are tightly bound. This close arrangement allows sound waves to transfer energy quickly from one particle to another, resulting in a higher speed of sound.
- **Liquids**: In liquids, particles are less tightly packed than in solids, which allows sound waves to travel, but not as quickly as in solids. The intermolecular forces are weaker than in solids, leading to a slower speed of sound.
- **Gases**: In gases, particles are far apart and move freely. The speed of sound is the slowest in gases because the energy transfer between particles is less efficient due to the larger distances between them.

3. **Conclusion**:
Based on the analysis, sound waves travel fastest in solids, followed by liquids, and slowest in gases. Sound cannot travel in a vacuum because there are no particles to transmit the sound waves.

4. **Final Answer**:
Therefore, the correct answer is that sound waves travel fastest in **solids**.