Choose the correct option for each question. There is only one correct response for each question.
What happens when the cutting edge of a knife is sharpened against a stone by rubbing on it?

Options

A. The microscopic irregularities present on the surface of the knife decrease
B. It changes the metal properties due to the heat produced by friction
C. It increases the friction offered by its surface
D. It increases the malleability of the knife.

Answer

To solve the question regarding what happens when the cutting edge of a knife is sharpened against a stone, we can break down the process step by step:

### Step-by-Step Solution:

1. **Understanding the Process of Sharpening**:
- When a knife is sharpened against a stone, it involves rubbing the knife's edge on the stone surface.

2. **Effect on the Knife's Edge**:
- This rubbing action removes material from the knife's edge, specifically the microscopic irregularities that are present on its surface.

3. **Reduction of Irregularities**:
- As the irregularities are removed, the surface of the knife becomes smoother. This smoothing process is crucial because it reduces the surface area that interlocks with other surfaces.

4. **Impact on Friction**:
- Friction between two surfaces is largely due to the interlocking of their microscopic irregularities. By reducing these irregularities, the interlocking is minimized, which leads to a decrease in friction.

5. **Resulting Sharpness**:
- With decreased friction, the knife can cut through materials more easily, making it sharper and more effective for cutting tasks.

6. **Conclusion**:
- Therefore, the correct option is that sharpening the knife reduces the irregularities on its surface, which in turn decreases the friction, allowing the knife to become sharp and efficient for cutting.