Answer
An acid removes OH⁻ ions from water.
A base removes H⁺ ions from water.
Step-by-step explanation
An acid is a chemical species that donates protons or hydrogen ions and/or accepts electrons. Most acids contain a hydrogen atom bonded that can release (dissociate) to yield a cation and an anion in water.
Hence, an acid removes OH- ions from water.
A base is a substance that results in an increase in the concentration of hydroxide ions when it is dissolved in water. Also, a base is a substance that when dissolved in water increases the number of hydroxide ions.
Therefore, a base removes H+ ions from water.