Answer : The correct option is, (1) [tex]OH^-[/tex] ions.
Explanation :
According to the Arrhenius concept, an acid is a type of substance which ionizes in water to gives [tex]H^+[/tex] ions (hydronium ions or hydrogen ions) and a base is a type of substance which ionizes in water to gives [tex]OH^-[/tex] ions (hydroxide ions).
As we know that KOH is a base which ionizes in water to gives [tex]OH^-[/tex] ions (hydroxide ions) and [tex]K^+[/tex] ions.
Hence, potassium hydroxide is classified as an Arrhenius base because KOH contains [tex]OH^-[/tex] ions.