Assertion (A) Colloidal solutions do not show Brownian motion.
Reason (R) Brownian motion is responsible for stability of sols.

Options

A. Assertion and reason both are correct and the reason is correct explanation of assertion.
B. Assertion and reason both are correct but reason does not explain assertion.
C. Assertion is correct, but reason is incorrect.
D. Assertion is incorrect, but reason is correct.

Explanation

To solve the question, we need to analyze both the assertion and the reason provided.

### Step-by-Step Solution:

1. **Understanding the Assertion**:
- The assertion states that "Colloidal solutions do not show Brownian motion."
- This statement is incorrect. Colloidal solutions do exhibit Brownian motion, which is the random movement of particles suspended in a fluid (liquid or gas) due to collisions with the molecules of the dispersion medium.

2. **Understanding the Reason**:
- The reason states that "Brownian motion is responsible for the stability of sols."
- This statement is correct. Brownian motion helps to keep the colloidal particles suspended and prevents them from settling down, thereby contributing to the stability of the colloidal solution.

3. **Conclusion**:
- Since the assertion is false (colloidal solutions do show Brownian motion) and the reason is true (Brownian motion does contribute to the stability of sols), we conclude that the correct answer is that the assertion is incorrect while the reason is correct.

4. **Final Answer**:
- Therefore, the correct option is D: Assertion is incorrect, but Reason is correct.