The surface of mortar and pestle (silbatta) used for grinding is etched again after long use to ___friction.

Options

A. keep same
B. remove
C. increase
D. decrease

Explanation

**Step-by-Step Solution:**

1. **Understanding the Function of Mortar and Pestle**: The mortar and pestle (silbatta) is used for grinding spices and other substances. The effectiveness of grinding depends on the friction between the pestle and the mortar.

2. **Observing Wear Over Time**: With prolonged use, the surface of the mortar and pestle becomes smooth due to the grinding action. This smoothness reduces the friction needed for effective grinding.

3. **Recognizing the Need for Roughness**: To maintain or improve the grinding efficiency, it is essential to have a rough surface. A rough surface increases friction, allowing for better grinding of spices.

4. **Etching the Surface**: To restore the roughness of the mortar and pestle after it has become smooth, the surface is etched. Etching creates small grooves and irregularities that enhance friction.

5. **Conclusion**: Therefore, the surface of the mortar and pestle is etched again after long use to increase friction, which is essential for effective grinding.

**Final Answer**: The surface of mortar and pestle (silbatta) used for grinding is etched again after long use to **increase friction**.

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