To sharpen the blade of a knife by rubbing it against a surface, which of the following will be most suitable?

To sharpen the blade of a knife, rubbing it against the surface of a stone will be the most suitable.

⇒ Friction increases when the surface is rough.

⇒ Stone has rough surface among all.

⇒ When you rub the knife against it, it will exert greater reaction.

⇒ As a result, the force of friction will increase and the knife will become sharper.