According to the Arrhenius concept, an acid is a type of substance which ionizes in water to gives ions (hydronium ions or hydrogen ions) and a base is a type of substance which ionizes in water to gives ions (hydroxide ions).
As we know that KOH is a base which ionizes in water to gives ions (hydroxide ions) and ions.
Hence, potassium hydroxide is classified as an Arrhenius base because KOH contains ions.
The answer is (1)OH- ions. The base has more OH- ions while the acid has more H+ ions. And if you dissolve them into water, the pH of the solution is also different. Base has pH>7 and acid has pH<7 at room temperature.