According to Arrhenius definition of acid bases: An acid donates [tex] H^{+} [/tex] ions in aqueous solution and a base donates hydroxide [tex] OH^{-} [/tex] ions in aqueous solution.
So the given statement that a substance that forms hydroxide ions in aquoeus solution is true.
Example of a base giving hydroxide ions in water:
[tex] NaOH (aq) ---> Na^{+}(aq) + OH^{-}(aq) [/tex]
