A(n) may be defined as a compound which contributes hydroxide ions or increases the oh- concentration when dissolved in water. acid

Arrhenius base

Explanation:

According to Arrhenius concept, a base is defined as a substance which donates hydroxide ions when dissolved in water and an acid is defined as a substance which donates hydronium ions in water.

According to the Bronsted Lowry conjugate acid-base theory, an acid is defined as a substance which donates protons and a base is defined as a substance which accepts protons.

According to the Lewis concept, an acid is defined as a substance that accepts electron pairs and base is defined as a substance which donates electron pairs.

A substance that increases the hydroxide ion concentration of a solution is an Arrhenius base.

i believe you are right for all except the 3rd ( look at sqdancefan his answer is much better)