The correct option is C aqueous
Arrhenius theory was confined only to aqueous solutions.
According to his Arrhenius theory, an acid is any compound or ion which yields hydrogen ions in water solution and a base is any compound or ion which yields hydroxyl ions in water solution.
Materials which dissolved in whole or in part as ions were, and still are, called electrolytes. A strong electrolyte, like sodium chloride, was a substance which dissociated completely into ions while a weak electrolyte remained partially in molecular form.