Answer:
A base is <u><em>A. a substance that increace the concentration of OH- ions in solution.</em></u>
Explanation:
According to Arrhenius Theory, a base is any substance that, when dissolved, releases hydroxyl ions (OH–). The bases are also known as alkalis, because when the hydroxyl groups dissociate and release, the pH of the solutions increases, that is, the solution becomes alkaline. Then its pH is greater than 7.
According to the Brønsted-Lowry Theory, a base is a substance capable of accepting protons (H +) in solution.
According to Lewis Theory, the bases are also considered those substances capable of donating or transferring electrons.
So, <u><em>a base is A. a substance that increace the concentration of OH- ions in solution.</em></u>
