Assertion : The compressibility of solids is less than that of gases and liquids.
Reason : There is tight coupling between the neighbouring atoms in solids.

Explanation

To solve the question regarding the assertion and reason about the compressibility of solids, let's break it down step by step.

### Step-by-Step Solution:

1. **Understanding the Assertion**:
- The assertion states that "The compressibility of solids is less than that of gases and liquids."
- Compressibility refers to the ability of a substance to decrease in volume under pressure.

2. **Comparing Compressibility**:
- In gases, the atoms are far apart and have a lot of empty space between them, making them highly compressible.
- In liquids, the atoms are closer together than in gases but still have some space to move, so they are less compressible than gases but more compressible than solids.
- In solids, the atoms are tightly packed together, meaning there is very little space to compress further. Thus, solids have the least compressibility.

3. **Conclusion on Assertion**:
- Since solids have the least compressibility compared to gases and liquids, the assertion is true.

4. **Understanding the Reason**:
- The reason states that "There is tight coupling between the neighboring atoms in solids."
- This tight coupling means that the atoms in solids are held together by strong intermolecular forces, which restrict their movement and make it difficult to compress the solid further.

5. **Conclusion on Reason**:
- The reason provided explains why solids are less compressible than gases and liquids. Therefore, the reason is also true.

6. **Final Evaluation**:
- Both the assertion and the reason are true, and the reason correctly explains the assertion.

### Final Answer:
- The correct option is that both the assertion and reason are true, and the reason is the correct explanation of the assertion.