Which term describes a substance that increases the concentration of hydroxide ions in solution?

Lewis definition of an acid

Arrhenius definition of a base

Bronsted-Lowry definition of a base

Bronsted-Lowry definition of an acid

Since the question pertains to hydroxide ions, or OH-, then we can be sure that the answer is a base. All we have to do is differentiate which of the definition is more appropriate. A Bronsted-Lowry base is defined as the substance that accepts a proton. An Arrhenius base is the substance that produces OH - during the acid-base reaction. Hence, the answer is Arrhenius definition base.