Strong base; $K^+$ and $OH^-$
Work Step by Step
Recall, a base forms $OH^-$ when dissolved while an acid forms $H^+$ when dissolved. In addition, strong acids/bases dissolve completely in water while weak ones only partially dissolve. (You simply have to memorize which bases/acids are strong and which are weak.) Using this, we find that this is a strong base. In order to find which ions are present, look for the cations (positive ions) and anions (negative ions) in the given substances. Recall, you may have to consider polyatomic ions, which are ions with multiple atoms that you need to memorize.