Assertion: The lightening conductor at the top of high building has sharp pointed ends.
Reason: The surface density of charge at sharp points is very high resulting in setting up of electric wind.

Options

A. Statement I is true, Statement II is True, Statement II is a correct explanation for statement I.
B. Statement I is true, Statement II is True, Statement II is Not a correct explanation for statement I.
C. Statement I is True, Statement II is False.
D. Statement I is False, Statement II is True.

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 "The lightning conductor at the top of a high building has sharp pointed ends."
- This is true because sharp pointed ends are designed to enhance the effectiveness of the lightning conductor.

**Hint**: Think about the physical design of lightning conductors and their purpose.

2. **Understanding the Reason**:
- The reason states that "The surface density of charge at sharp points is very high resulting in setting up of electric wind."
- This is also true. The sharp points of the conductor lead to a high surface charge density due to the geometry of the conductor. According to electrostatics, the surface charge density (σ) is inversely proportional to the radius of curvature (r) of the conductor. Therefore, at sharp points (where r is small), σ becomes very large.

**Hint**: Recall the relationship between surface charge density and the radius of curvature.

3. **Connecting the Assertion and Reason**:
- The high surface charge density at the sharp points leads to a stronger electric field in the surrounding air. This can ionize the air and create what is known as "electric wind," which can help in discharging the accumulated charge from the clouds.
- This means that the reason provided explains why the assertion is true.

**Hint**: Consider how electric fields interact with the surrounding environment.

4. **Conclusion**:
- Since both the assertion and the reason are true, and the reason correctly explains the assertion, we conclude that both statements are correct and the reason is the correct explanation for the assertion.

**Hint**: Think about the logical relationship between the two statements.

### Final Answer:
Both the assertion and the reason are true, and the reason is the correct explanation for the assertion.