Answer : The correct option is, (4) hydroxide ion
Explanation :
According to the Arrhenius acid-base theory, an acid is a substance that ionizes in the aqueous solution to give hydronium ion or hydrogen ion
and a bases is a substance that ionizes in the aqueous solution to give hydroxide ion
.
As per question, hydroxide ion is the only negative ion present in an aqueous solution of an Arrhenius base and hydrogen or hydronium ion is the only positive ion present in an aqueous solution of an Arrhenius acid.
Hence, the correct option is, (4) hydroxide ion